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atom

atom

atom Sentence Examples

  • An atom is made up of protons, neutrons, and electrons.

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  • When an atom is charged, it becomes an ion.

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  • There's not an atom of dirt in her house because she never stops cleaning.

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  • A molecule may be defined as the smallest part of a substance which can exist alone; an atom as the smallest part of a substance which can exist in combination.

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  • Dalton believed that the molecules of the elementary gases consisted each of one atom; his diagram for hydrogen gas makes the point clear.

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  • It was against them that was broken his invincible will, sweeping away in the defeat the work of Panama, his own fortune, his fame and almost an atom of his honour.

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  • I couldn't find an atom of hatred in the sweet, innocent girl.

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  • What atom is most prevalent in Earth's atmosphere?

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  • CH(CH 3) CH 3, isobutane, substitution occurring at the medial atom.

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  • Torbern Olof Bergman used an elaborate system in his Opuscula physica et chemica (1783); the 1 Dalton's atomic theory is treated in more detail in the article Atom.

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  • This compound may be considered as derived from methane, CH 4, by replacing a hydrogen atom by the monovalent group CH 3, known as methyl; hence ethane may be named " methylmethane."

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  • CH3, known as " normal " or n-butane, substitution occurring at a terminal atom, or CH 3.

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  • (methylene) groups and the molecule consists of a single chain; such hydrocarbons are referred to as being normal; (2) has a branch and contains the group; CH (methine) in which the free valencies are attached to carbon atoms; such hydrocarbons are termed secondary or iso-; (3) is characterized by a carbon atom linked directly to four other carbon atoms; such hydrocarbons are known as tertiary.

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  • It will be seen that each type depends upon a specific radical or atom, and the copulation of this character with any hydrocarbon radical (open or cyclic) gives origin to a compound of the same class.

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  • An important class of compounds, termed amines (q.v.), results from the condensation of alcohols with ammonia, water being eliminated between the alcoholic hydroxyl group and a hydrogen atom of the ammonia.

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  • Assuming the four valencies of the carbon atom to be directed from the centre of a regular tetrahedron towards its four corners, the angle at which they meet.

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  • As an illustration it may be pointed out that in the case of the two known types of lactones - the y-lactones, which contain four carbon atoms and one oxygen atom in the ring, are more readily formed and more stable (less readily hydrolysed) than the S-lactones, which contain one oxygen and five carbon atoms in the ring.

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  • The ringed structure of benzene, C 6 H 61 was first suggested in 1865 by August Kekule, who represented the molecule by six CH groups placed at the six angles of a regular hexagon, the sides of which denoted the valencies saturated by adjacent carbon atoms, the fourth valencies of each carbon atom being represented as saturated along alternate sides.

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  • This symbol is in general use; it is assumed that at each corner there is a CH group which, however, is not always written in; if a hydrogen atom be substituted by another group, then this group is attached to the corner previously occupied by the displaced hydrogen.

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  • The amines also exhibit striking differences: in the aliphatic series these compounds may be directly formed from the alkyl haloids and ammonia, but in the benzene series this reaction is quite impossible unless the haloid atom be weakened by the presence of other substituents, e.g.

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  • These results may be graphically represented as follows: numbering the hydrogen atoms in cyclical order from i to 6, then the first thesis demands that whichever atom is substituted the same compound results, while the second thesis points out that the pairs 2 and 6, and 3 and 5 are symmetrical with respect to 1, or in other words, the di-substitution derivatives 1.2 and 1.6, and also 1.3 and 1.5 are identical.

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  • The proof is divided into two parts: (1) that four hydrogen atoms are equal, and (2) that two pairs of hydrogen atoms are symmetrical with reference to a specified hydrogen atom.

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  • From meta-brombenzoicacid two nitrobrombenzoic ac i ds are obtained on direct nitration; elimination of the bromine atom and the reduction of the nitro to an amino group in these two acids results in the formation of the same ortho-aminobenzoic acid.

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  • Intermolecular transformations-migrations of substituent groups from one carbon atom to anotherare of fairly common occurrence among oxy compounds at elevated temperatures.

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  • He assumed that if we have one atom 1 It is now established that ortho compounds do exist in isomeric forms, instances being provided by chlor-, brom-, and amino-toluene, chlorphenol, and chloraniline; but arguments, e.g.

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  • Applying this notion to benzene, let us consider the impacts made by the carbon atom (I) which we will assume to be doubly linked to the carbon atom (2) and singly linked to (6), h standing for the hydrogen atom.

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  • This implied that in the benzene complex there was at least one carbon atom linked to three others, thus rendering Kekule's formula impossible and Ladenburg's and Claus' possible.

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  • Thiele suggested a doctrine of " partial valencies," which assumes that in addition to the ordinary valencies, each doubly linked atom has a partial valency, by which the atom first interacts.

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  • Zeit., 1905, 29, p. 30), assumed the six carbon atoms to occupy six of the corners of a cube, each carbon atom being linked to a hydrogen atom and by single bonds to two neighbouring carbon atoms, the remaining valencies being directed to the unoccupied corners of the cube, three to each, where they are supposed to satisfy each other.

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  • The formula has the advantage that it may be constructed from tetrahedral models of the carbon atom; but it involves the assumption that the molecule has within it a mechanism, equivalent in a measure to a system of railway points, which can readily close up and pass into that characteristic of benzene.

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  • Similarly a CH group may be replaced by a nitrogen atom with the production of compounds of similar stability; thus benzene gives pyridine, naphthalene gives quinoline and isoquinoline; anthracene gives acridine and a and 3 anthrapyridines.

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  • The transition between the two classes as differentiated above may be illustrated by the following cyclic compounds, each of which contains a ring composed of four carbon atoms and one oxygen atom: CH CH/ CH CH/ CH CO I CH CO' CH =CH c Tetramethylene But yrolactone.

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  • Six-membered ring systems can be referred back, in a manner similar to the above, to pyrone, penthiophene and pyridine, the substances containing a ring of five carbon atoms, and an oxygen, sulphur and nitrogen atom respectively.

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  • the amount which is equivalent to one part of hydrogen; and (2) a factor which denotes the number of atoms of hydrogen which combines with or is equivalent to one atom of the particular element.

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  • The substitution of a hydrogen atom by the hydroxyl group generally occasions a rise in boiling-point at about Ioo°.

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  • Soc., 18 93, 6 3, p. 465) states, that the melting-point of any odd member of a homologous series is lower than the melting-point of the even member containing one carbon atom less.

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  • The identity of the four valencies of the carbon atom follows from the fact that the heats of combustion of methane, ethane, propane, trimethyl methane, and tetramethyl methane, have a constant difference in the order given, viz.

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  • 158.6 calories; this means that the replacement of a hydrogen atom by a methyl group is attended by a constant increase in the heat of combustion.

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  • Theabsolute heat of combustion of a carbon atom is therefore 135.34 calories, and this is independent of the form of the carbon burned.

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  • We assume that each carbon atom and each hydrogen atom contributes equally to the thermal effect.

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  • It is remarkable that the difference in the heats of formation of ketones and the paraffin containing one carbon atom less is 67.94 calories, which is the heat of formation of carbon monoxide at constant volume.

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  • Thus oxygen varies according as whether it is linked to hydrogen (hydroxylic oxygen), to two atoms of carbon (ether oxygen), or to one carbon atom (carbonyl oxygen); similarly, carbon varies according as whether it is singly, doubly, or trebly bound to carbon atoms.

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  • Baeyer has suggested that the nine carbon atom system of xanthone may act as a chromophore.

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  • An alternative view, due to Green, is that the oxygen atom of the xanthone ring is tetravalent, a supposition which permits the formulation of these substances as ortho-quinonoids.

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  • The chlorine atom in this compound is replaced by the cyano-group, which is then reduced to the CH 2 NH 2.

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  • Beckmann, Ber., 1886, 1 9, p. 9 8 9; 188 7, 20, p. 2580), yielding as final products an acid-amide or anilide, thus: RC(:N OH)R'-RC(OH) :NR' ---> As regards the constitution of the oximes, two possibilities exist, namely >C: NOH, or > C' ?, and the first of these is presumably correct, since on alkylation and subsequent hydrolysis an alkyl hydroxylamine of the type NH 2 OR is obtained, and consequently it is to be presumed that in the alkylated oxime, the alkyl group is attached to oxygen, and the oxime itself therefore contains the hydroxyl group. It is to be noted that the oximes of aromatic aldehydes and of unsymmetrical aromatic ketones frequently exist in isomeric forms. This isomerism is explained by the HantzschWerner hypothesis (Ber., 1890, 23, p. II) in which the assumption is made that the three valencies of the nitrogen atom do not lie in the same plane.

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  • , the former, N OH HO N where the H atom and OH group are contiguous, being known as syn-aldoximes and the latter as the anti-aldoximes.

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  • -> CH3C6H5CONHC6H51 N OH Syn-phenyltolylketoxime CH3 C6H4 C C6H5 CH3C6H4NH000,H5 HO N A nti-tolylphenylketoxime In the case of the aldoximes, that one which most readily loses the elements of water on dehydration is assumed to contain its hydroxyl radical adjacent to the movable hydrogen atom and is designated the syn-compound.

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  • Here the ions are potassium and the group Ag(CN)2.1 Each potassium ion as it reaches the cathode precipitates silver by reacting with the solution in accordance with the chemical equation K--+KAg(CN) 2 =2KCN+Ag, while the anion Ag(CN) 2 dissolves an atom of silver from the anode, and re-forms the complex cyanide KAg(CN) 2 by combining with the 2KCN produced in the reaction described in the equation.

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  • In metals the electrons can slip from one atom to the next, since a current can pass without chemical action.

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  • When a current passes from an electrolyte to a metal, the electron must be detached from the atom it was accompanying and chemical action be manifested at the electrode.

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  • The aldehyde group reacts with hydrocyanic acid to produce two stereo-isomeric cyanhydrins; this isomerism is due to the conversion of an originally non-asymmetric carbon atom into an asymmetric one.

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  • Since the molecule contains an asymmetric carbon atom, the acid exists in three forms, one being an inactive "racemic" mixture, and the other two being optically active forms. The inactive variety is known as paramandelic acid.

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  • The mass of each is about 3 7 1 o T th part of that of a hydrogen atom, and with each is indissolubly associated a charge of negative electricity equal to about 3.1 Xio '° C.G.S.

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  • An electrically neutral atom is believed to be constituted in part, or perhaps entirely, of a definite number of electrons in rapid motion within a " sphere of uniform positive electrification " not yet explained.

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  • One or more of the electrons may be detached from the system by a finite force, the number so detachable depending on the valency of the atom; if the atom loses an electron, it becomes positively electrified; if it receives additional electrons, it is negatively electrified.

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  • Mag., 1881, 11, 387) pointed out that this latter constituted the indivisible " atom of electricity " or natural unit charge.

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  • The hydrogen in the primary and secondary nitro compounds which is attached to the same carbon atom as the nitro group is readily replaced by bromine in alkaline solution.

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  • The pseudo-nitrols, RR':C(NO)(NO 2), may be obtained by the action of nitrous acid on the secondary nitroparaffins; by the action of silver nitrite on such bromnitrosoparaffins as contain the bromine and the nitroso group united to the same carbon atom (0.

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  • Piperic acid differs from piperonylic acid by the group C4H 4, and it was apparent that these carbon atoms must be attached to the carbon atom which appears in the carboxyl group of piperonylic acid, for if they were directly attached to the benzene ring polycarboxylic acids would result in oxidation.

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  • Toxins may thus become so closely keyed into their corresponding atom groups, as for instance in tetanus, that they are no longer free to combine with the antitoxin; or, again, an antitoxin injected before a toxin may anticipate it and, preventing its mischievous adhesion, dismiss it for excretion.

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  • Formic acid yields acridine, and the higher homologues give derivatives substituted at the meso carbon atom, N N +[[Hcooh-C 6 H 5 /Inc6h5->C6h4 C6h4 Cho Ch N N +Ch 3 000h->C 6 H 5 /IC 6 H 5 --C 6 H 4 C6h4 Coch 3 C]](CH3) Acridine may also 1:e obtained by passing the vapour of phenylortho-toluidine through a red-hot tube (C. Graebe, Ber., 1884, 17, p. 1 37 0); by condensing diphenylamine with chloroform, in presence of aluminium chloride (0.

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  • The organic derivatives of silicon resemble the corresponding carbon compounds except in so far that the silicon atom is not capable of combining with itself to form a complex chain in the same manner as the carbon atom, the limit at present being a chain of three silicon atoms. Many of the earlier-known silicon alkyl compounds were isolated by Friedel and Crafts and by Ladenburg, the method adopted consisting in the interaction of the zinc alkyl compounds with silicon halides or esters of silicic acids.

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  • Most metals form carbonates (aluminium and chromium are exceptions), the alkali metals yielding both acid and normal carbonates of the types Mhco 3 and M 2 CO 3 (M = one atom of a monovalent metal); whilst bismuth, copper and magnesium appear only to form basic carbonates.

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  • He held the doctrine that the chemical elements are compounds of equal and similar atoms, and might therefore possibly be all derived from one generic atom.

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  • The facts suggested that the six carbon atoms formed a chain, and that a hydroxy group was attached to five of them, for it is very rare for two hydroxy groups to be attached to the same carbon atom.

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  • The remaining oxygen atom is aldehydic or ketonic, for the sugars combine with hydrocyanic acid, hydroxylamine and phenylhydrazine.

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  • - The cyanhydrins on hydrolysis give monocarboxylic acids, which yield lactones; these compounds when reduced by sodium amalgam in sulphuric acid solution yield a sugar containing one more carbon atom.

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  • The identity of the formulae and osazones of d-mannose and d-glucose showed that the stereochemical differences were situated at the carbon atom adjacent to the aldehyde group. Fischer applied a method indicated by Pasteur in converting dextro into laevo-tartaric acid; he found that both d-mannonic and d-gluconic acids (the latter is yielded by glucose on oxidation) were mutually convertible by heating with quinoline under pressure at 140°.

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  • Although containing an asymmetric carbon atom it has not been resolved.

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  • Employing the notation in which the molecule is represented vertically with the aldehyde group at the bottom, and calling a carbon atom+or - according as the hydrogen atom is to the left or right, the possible configurations are shown in the diagram.

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  • When such compounds are converted into corresponding dibasic acids, CO 2 H.[CH(OH)) 3.00 2 H, the number of asymmetric carbon atoms becomes reduced from three to two, as the central carbon atom is then no longer associated with four, but with only three different radicles.

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  • The replacement of one hydrogen atom by one alkyl or aryl group gives rise to primary amines; of two hydrogen atoms by two groups, to secondary amines; of three hydrogen atoms by three groups, to tertiary amines.

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  • If the nitrogen atom in the quaternary ammonium salts be in combination with four different groups, then the molecule is asymmetrical, and the salt can be resolved into optically active enantiamorphous isomerides.

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  • Since the acid contains an asymmetric carbon atom, it can exist in three forms, a dextro-rotatory, a laevo-rotatory and an inactive form; the acid obtained in the various synthetical processes is the inactive form.

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  • OH, termed the carboxyl group, in which the hydrogen atom is replaceable by metals with the formation of salts, and by alkyl radicals with the formation of esters.

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  • Their experiments, although not conclusive, appear to indicate that the molecule of a metal when in dilute solution often consists of one atom.

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  • Sir Edward Frankland,showed how it could be derived from, and converted into, ethane; and thus determined it to be ethane in which one hydrogen atom was replaced by a hydroxyl group. Its constitutional formula is therefore CH3�CH2.OH.

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  • Rutherford had announced the nuclear theory of atomic structure which required each atom to consist of a minute positively charged nucleus about which negative electrons were distributed.

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  • This number is probably to be identified with the electric charge upon the nucleus of the atom.

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  • The word appears to have been invented during the 17th century, and remained synonymous with " atom " (Gr.

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  • " Atom " has mainly a chemical import, being defined as the smallest particle of matter which can take part in a chemical reaction; a " molecule " is composed of atoms, generally two or more.

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  • For the detailed chemical significance of these terms, see Chemistry; and for the atomic theory of the chemist (as distinguished from the atomic or molecular theory of the physicist) see Atom; reference may also be made to the article Matter.

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  • The leading historical stages in the evolution of the modern conception of the molecular structure of matter are treated in the following passage from James Clerk Maxwell's article Atom in the 9th edition of the Ency.

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  • " Atom 1 (iiTopos) is a body which cannot be cut in two.

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  • " The atomists assert that after a certain number of such divisions the parts would be no longer divisible, because each of them would be an atom.

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  • If it were not so, Lucretius tells us, there could be no motion, for the atom which gives way first must have some empty place to move into.

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  • " The opposite school maintained then, as they have always done, 1 It wiII be noted that Clerk Maxwell's " atom " and " atomic theory " have the significance which we now attach to " molecule " and " molecular theory."

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  • According to Boscovich matter is made up of atoms. Each atom is an indivisible point, having position in space, capable of motion in a continuous path, and possessing a certain mass, whereby a certain amount of force is required to produce a given change of motion.

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  • Besides this the atom is endowed with potential force, that is to say, that any two atoms attract or repel each other with a force depending on their distance apart.

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  • " Thus, in Boscovich's theory, the atom has continuity of existence in time and space.

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  • On the other hand, the atom itself has no parts or dimensions.

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  • Now if the atoms are regarded as points or spherical bodies oscillating about positions of equilibrium, the value of n+3 is precisely six, for we can express the energy of the atom in the form (9 2 v a 2 v a2v E = z(mu 2 +mv 2 +mw 2 +x 2 ax2 + y2ay2-fz2az2), where V is the potential and x, y, z are the displacements of the atom referred to a certain set of orthogonal axes.

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  • The difficulty is further diminished when it is proved, as it can be proved, 2 that the modes of energy represented in the atomic spectrum acquire energy so slowly that the atom might undergo collisions with other atoms for centuries before being set into oscillations which would possess an appreciable amount of energy.

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  • The other course is to consider matter as formed of ultimate atoms, each the nucleus or core of an intrinsic modification impressed on the surrounding region of the aether; this might conceivably be of the nature of vortical motion of a liquid round a ring-core, thus giving a vortex atom, or of an intrinsic strain of some sort radiating from a core, which would give an electric atom.

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  • We recognize an atom only through its physical activities, as manifested in its interactions with other atoms at a distance from it; this field of physical activity would be identical with the surrounding field of aethereal motion or strain that is inseparably associated with the nucleus, and is carried on along with it as it moves.

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  • An important question arises whether, when a material body is moved through the aether, the nucleus of each atom carries some of the surrounding aether along with it; or whether it practically only carries on its strain-form or physical atmosphere, which is transferred from one portion of aether to another after the manner of a shadow, or rather like a loose knot which can slip along a rope without the rope being required to go with it.

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  • A dielectric substance is electrically polarized by a field of electric force, the atomic poles being made up of the displaced positive and negative intrinsic charges in the atom: the polarization per unit volume (f',g',h') may be defined on the analogy of magnetism, and d/dt(f',g',h') thus constitutes true electric current of polarization, i.e.

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  • The establishment and convection of a single polar atom constitutes in fact a quasi-magnetization, in addition to the polarization current as above defined, the negative poles completing the current circuits of the positive ones.

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  • As unsaturated compounds they can combine with two monovalent atoms. Hydrogen is absorbed readily at ordinary temperature in the presence of platinum black, and paraffins are formed; the halogens (chlorine and bromine) combine directly with them, giving dihalogen substituted compounds; the halogen halides to form monohalogen derivatives (hydriodic acid reacts most readily, hydrochloric acid, least); and it is to be noted that the haloid acids attach themselves in such a manner that the halogen atom unites itself to the carbon atom which is in combination with the fewest hydrogen atoms (W.

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  • Sand, Ber., 1900, 33, pp. 1 34 0 et seq.), and those with a tertiary carbon atom yield double salts with zinc chloride.

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  • Chemie, 1867, 3, p. 39), ascribes to the molecule a peroxide configuration which accounts for its oxidizing powers but not for the fact that each oxygen atom is capable of replacement by one atom of chlorine.

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  • " To the naked eye it looked like a little black atom darting about in a most wonderful manner."

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  • - Hydrocyanic acid forms two series of derivatives by the exchange of its hydrogen atom for alkyl or aryl groups; namely the nitriles, of type R CN, and the isonitriles, of type R NC. The latter compounds may be considered as derivatives of the as yet unknown isohydrocyanic acid HNC.

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  • This reaction shows that the alkyl or aryl group is attached to the carbon atom in the nitrile.

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  • This reaction shows that the alkyl or aryl group is linked to the nitrogen atom.

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  • The carbon atom in the isonitriles is assumed by J.

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  • Nef to be divalent, since these substances readily form addition compounds, such addition taking place on the carbon atom, as is shown by the products of hydrolysis; for example with ethyl carbylamine: C 2 H 5 NC -FCH 3 C0C1--> C 2 H 5 NC(00CH 3)CI -->HCI -{- C2H5NH3 -fCH3CO C02H.

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  • Such a reaction can only take place if the addition of the alkyl group takes place on the nitrogen atom of the isonitrile, from which it follows that the nitrogen atom must be trivalent and consequently the carbon atom divalent.

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  • On the other hand, when there is but little electro-chemical difference between the radical of the cyanide and that of the reacting compound then the nitrogen atom is the more unsaturated element and.

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  • Chromium salts readily combine with ammonia to form complex salts in which the ammonia molecule is in direct combination with the chromium atom.

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  • Acid anhydrides replace the imino-hydrogen atom by acidyl radicals, and boiling with water converts them into phenols.

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  • The electrons responsible for the radiation are probably few and not directly involved in the structure of the atom, which according to the view at present in favour, is itself made up of electrons.

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  • As there is undoubtedly a connexion between thermal motion and radiation, the energy of these electrons within the atom must be supposed to increase with temperature.

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  • highest temperatures at our command it is small compared with the energy of translatory motion, but as the temperature increases, it must ultimately gain the upper hand, and if there is anywhere such a temperature as that of several million degrees, the greater part of the total energy of a body will be outside the atom and molecular motion ultimately becomes negligible compared with it.

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  • Considering the complexity of the subject it is not surprising that the efforts to connect theoretically the possible periods of the atom considered as a vibrating system have met with no considerable success.

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  • The one endeavours to determine the conditions, which are consistent with our knowledge of atomic constitution derived from other sources, and lead to systems of vibration similar to those of the actual atom.

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  • Jeans, 2 who showed that a shell-like constitution of the atom, the shells being electrically charged, 1 Proc. Roy.

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  • On the whole it seems probable that the system of moving electrons, which according to a modern theory constitute the atom, is not directly concerned in thermal radiation which would rather be due to a few more loosely connected electrons hanging on to the atom.

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  • The difficulty that a number of spectroscopic lines seem to involve at least an equal number of electrons may be got over by imagining that the atom may present several positions of equilibrium to the electron, which it may occupy in turn.

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  • Such spectra seem to be characteristic of complex molecular structure, as they appear when compounds are raised to incandescence without decomposition, or when we examine the absorption spectra of vapours such as iodine and bromine and other cases where we know that the molecule consists of more than one atom.

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  • At the same time his synechological view prevented him from saying that every atom has a soul, because according to him a soul always corresponds to a unity of a physical manifold.

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  • See Henry, Life of Dalton, Cavendish Society (1854); Angus Smith, Memoir of John Dalton and History of the Atomic Theory (1856), which on pp. 253-263 gives a list of Dalton's publications; and Roscoe and Harden, A New View of the Origin of Dalton's Atomic Theory (1896); also Atom.

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  • Blagden (Ber.,1900,33,p.2544), who consider that three simultaneous reactions occur, namely, the formation of labile double salts which decompose in such a fashion that the radical attached to the copper atom wanders to the aromatic nucleus; a catalytic action, in which nitrogen is eliminated and the acid radical attaches itself to the aromatic nucleus; and finally, the formation of azo compounds.

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  • This change only occurs when the halogen atom is in the orthoor paraposition to the - N2 - group.

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  • Hantzsch, Ber., This assumption also shows the relationship of the diazonium hydroxides to other quaternary ammonium compounds, for most of the quaternary ammonium hydroxides (except such as have the nitrogen atom attached to four saturated hydrocarbon radicals) are unstable, and readily pass over into compounds in which the hydroxyl group is no longer attached to the amine nitrogen; thus the syn-diazo hydroxides are to be regarded as pseudo-diazonium derivatives.

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  • In the case of metamerism we can imagine that the atoms are differently linked, say in the case of butylene that the atoms of carbon are joined together as a continuous chain, expressed by CC C C, normally as it is called, whereas in isobutylene the fourth atom of carbon is not attached to the third but to the second carbon atom, i.e.

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  • The cases of mutual transformation are generally characterized by the fact that in the compound of higher molecular weight no new links of carbon with carbon are introduced, the trioxymethylene being O CH2-0 CH 2 whereas honey-sugar correg probably C C H 2 -0% sponds to CH 2 0H [[Choh Choh Choh Choh Cho]], each point representing a linking of the carbon atom to the next.

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  • As carbon tends to hold the atom attached to it, one may presume that this property expresses itself in a predominant way where the other element is carbon also, and so the linkage represented by -C-C-is one of the most difficult to loosen.

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  • In this case it is readily seen that isomerism introduces itself in the three carbon atom derivative: the propyl alcohols, expressed by the formulae CH 3 CH2 CH 2 0HandCH 3 CHOH CH3, are known as propyl and isopropyl alcohol respectively.

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  • Frankland, when in 1858 Kekule published a paper in which, after giving reasons for regarding carbon as a tetravalent element, he set forth the essential features of his famous doctrine of the linking of atoms. He explained that in substances containing several carbon atoms it must be assumed that some of the affinities of each carbon atom are bound by the affinities of the atoms of other elements contained in the substance, and some by an equal number of the affinities of the other carbon atoms. The simplest case is when two carbon atoms are combined so that one affinity of the one is tied to one affinity of the other; two, therefore, of the affinities of the two atoms are occupied in keeping the two atoms together, and only the remaining six are available for atoms of other elements.

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  • The high conductivity of metals is then explained by the small mass and high velocity of diffusion of these electric atoms. Assuming the kinetic energy of an electric atom at any temperature to be equal to that of a gaseous molecule, its velocity, on Sir J.

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  • VALERIC ACID, or [[Valerianic Acid, C4h9 C02h]], an organic acid belonging to the fatty acid series, which exists in four isomeric forms, one of which contains an asymmetric carbon atom and consequently occurs in two optically active modifications and one optically inactive modification.

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  • Walden point out from the physico-chemical standpoint that in water and hydrogen peroxide the oxygen atom is probably quadrivalent.

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  • A Hypothesis Doubtfully Attributed To Maxwell Is That Each Additional Atom In The Molecule Is Equivalent To Two Extra Degrees Of Freedom.

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  • The Ideal Atomic Heat Is The Thermal Capacity Of A Gramme Atom In The Ideal State Of Monatomic Gas At Constant Volume.

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  • For the so-called "disintegration of the thorium atom" and the relation of this element to the general subject of radio-active emanations, see Radio-Activity.

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  • The imino hydrogen atom is easily replaced by metals.

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  • about drcith part of the mass of a hydrogen atom."

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  • The subject was pursued by Thomson and the Cambridge physicists with great mathematical and experimental ability, and finally the conclusion was reached that in a high vacuum tube the electric charge is carried by particles which have a mass only a fraction, as above mentioned, of that of the hydrogen atom, but which carry a charge equal to the unit electric charge of the hydrogen ion as found by electrochemical researches.

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  • 2 Later results show that the mass of a hydrogen atom is not far from I.

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  • The diameter of a chemical atom is of the order of z07 centimetre.

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  • The final outcome of these investigations was the hypothesis that Thomson's corpuscles or particles composing the cathode discharge in a high vacuum tube must be looked upon as the ultimate constituent of what we call negative electricity; in other words, they are atoms of negative electricity, possessing, however, inertia, and these negative electrons are components at any rate of the chemical atom.

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  • For the hydrogen atom the ratio of charge to mass as deduced from electrolysis is about Io 1.

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  • Hence the mass of an electron is y ff l iT uth of that of a hydrogen atom.

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  • Thomson also developed this hypothesis in a profoundly interesting manner, and we may therefore summarize very briefly the views held on the nature of electricity and matter at the beginning of the 10th century by saying that the term electricity had come to be regarded, in part at least, as a collective name for electrons, which in turn must be considered as constituents of the chemical atom, furthermore as centres of certain lines of self-locked and permanent strain existing in the universal aether or electromagnetic medium.

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  • Wislicenus found that only one hydrogen atom in the -CH 2 - group is directly replaceable by sodium, and that if the sodium be then replaced by an alkyl group, the second hydrogen atom in the group can be replaced in the same manner.

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  • OXAZOLES, a group of organic compounds containing a ring complex (shown below) composed of three carbon atoms, and one oxygen and one nitrogen atom; they are isomeric with the isoxazoles.

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  • Compounds of antimony with all the halogen elements are known, one atom of the metal combining with three or five atoms of the halogen, except in the case of bromine, where only the tribromide is known.

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  • In other cases such changes cannot be detected, and the only evidence of their occurrence may be the associated symptoms. The very important work of Ehrlich on diphtheria toxin shows that in the molecule of toxin there are at least two chief atom groups - one, the " haptophorous," by which the toxin molecule is attached to the cell protoplasm; and the other the " toxophorous," which has a ferment-like action on the living molecule, producing a disturbance which results in the toxic symptoms. On this theory, susceptibility to a toxin will imply both a chemical affinity of certain tissues for the toxin molecule and also sensitiveness to its actions, and, furthermore, non-susceptibility may result from the absence of either of these two properties.

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  • Living protoplasm, or in other words a biogen molecule, is regarded as consisting of a central atom group (Leistungskern), related to which are numerous secondary atom groups or sidechains, with unsatisfied chemical affinities.

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  • - Democritus devoted considerable attention to the structure of the human body, the noblest portion of which he considered to be the soul, which everywhere pervades it, a psychic atom being intercalated between two corporeal atoms. Although, in accordance with his principles, Democritus was bound to regard the soul as material (composed of round, smooth, specially mobile atoms, identified with the fire-atoms floating in the air), he admitted a distinction between it and the body, and is even said to have looked upon it as something divine.

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  • When potassium iodide is added to a solution of cupric acetate, the reaction (Cu(C 2 H 3 0 2) 2 + 2KI= Cul + 2K(C 2 H 3 0 2) + I takes place; that is, for each atom of copper one atom of iodine is liberated.

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  • Pollock, "the conception is that mind is the one ultimate reality; not mind as we know it in the complex forms of conscious feeling and thought, but the simpler elements out of which thought and feeling are built up. The hypothetical ultimate element of mind, or atom of mind-stuff, precisely corresponds to the hypothetical atom of matter, being the ultimate fact of which the material atom is the phenomenon.

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  • The subject has been especially studied by Skraup, Konigs, and von Miller; Kiinigs and von Miller have proposed formulae consisting of a piperidine ring substituted with a vinyl group; in the former that is a bridge of CH 2 C(OH) from the nitrogen atom to the -y-carbon atom, connexion with the quinoline residue being made at the hydroxylic carbon atom through a CH2 group: whilst in the latter the piperidine ring is substituted by a methyl group in addition to the vinyl group and the bridge is simply C(OH), with which connexion is made as before.

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  • A source which seems plausible, perhaps only because it is less easy to test, is rearrangement of the structure of the elements' atoms. An atom is no longer figured as indivisible, it is made up of more or less complex, and more or less permanent, systems in internal circulation.

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  • If the sources of energy within the atom can be drawn upon, and the phenomena of radio-activity leave no doubt about this, there is here an incalculable source of heat which takes the cogency out of any other calculation respecting the sources maintaining the sun's radiation.

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  • It is worthy of notice that while many metals dissolve in cold dilute sulphuric acid, with the liberation of hydrogen, in accordance with the typical equation: M -{- H 2 50 4 = MSO 4 -1H2 (M denoting one atom of divalent or two atoms of a monovalent metal), there are several (copper, mercury, antimony, tin, lead and silver) which are insoluble in the cold dilute acid, but dissolve in the hot strong acid with evolution of sulphur dioxide, thus: M -}- 2H 2 250 4 = MSO 4 SO 2 + 2H 2 0.

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  • Na 0 0 Na, Bab, which yield hydrogen peroxide with acids; and (2) the polyoxides, having the oxygen atoms doubly linked to the metallic atom, e.g.

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  • Alcohols are classified on two distinct principles, one depending upon the number of hydroxyl groups present, the other on the nature of the remaining groups attached to the carbon atom which carries the hydroxyl group. Monatomic or monohydric alcohols contain only one hydroxyl group; diatomic, two, known as glycols; triatomic, three, known as glycerols; and so on.

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  • Propane, CH 3 CH 2 CH 3, can give rise to two alcohols - a primary alcohol, CH 3 CH 2 CH 2 OH (normal propyl alcohol), formed by replacing a hydrogen atom attached to a terminal carbon atom, and a secondary alcohol, CH 3.

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  • CH(OH) � CH 3 (isopropyl alcohol), when the substitution is effected on the middle carbon atom.

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  • Each of these hydro-carbons gives rise to two alcohols: n-butane gives a primary and a secondary; and iso-butane a primary, when the substitution takes place in one of the methyl groups, and a tertiary, when the hydrogen atom of the: CH group is substituted.

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  • Tertiary alcohols are thus seen to be characterized by the group C � OH, in which the residual valencies of the carbon atom are attached to alkyl groups.

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  • Regarding methyl alcohol, for which he proposed the name carbinol, as the simplest alcohol, he showed that by replacing one hydrogen atom of the methyl group by an alkyl residue, compounds of the general formula R�CH 2 �OH would result.

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  • The sneers of Horace Walpole, and the savage attack of Smollett in The Adventures of an Atom, are animated by personal or political spite.

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  • The chlorides AsCl2CH3 and AsCl(CH3)2 as well as As(CH3)3 are capable of combining with two atoms of chlorine, the arsenic atom apparently changing from the tri- to the penta-valent condition, and the corresponding oxygen compounds can also be oxidized to compounds containing one oxygen atom or two hydroxyl groups more, forming acids or oxides.

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  • The series will thus possess the following general formulae M 2 CrO 4 M2Cr207 M2Cr30,0 &c. (M =one atom of a normal chromate bichromate trichromate monovalent metal.) Chromates.

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  • It is impossible within brief limits to convey more than a general idea of the work of a philosopher who published more than three hundred original papers bearing upon nearly every branch of physical science; who one day was working out the mathematics of a vortex theory of matter on hydrodynamical principles or discovering the limitations of the capabilities of the vortex atom, on another was applying the theory of elasticity to tides in the solid earth, or was calculating the size of water molecules, and later was designing an electricity meter, a dynamo or a domestic water-tap. It is only by reference to his published papers that any approximate conception can be formed of his life's work; but the student who had read all these knew comparatively little of Lord Kelvin if he had not talked with him face to face.

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  • When discussing the atom bomb, mass destruction springs to mind.

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  • A significant fraction of the oxy radical also reacts via hydrogen atom abstraction from the added reagent.

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  • acceptor atom, lifetime or leave unsorted.

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  • The presence of that hydrogen atom makes aldehydes very easy to oxidize.

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  • If at least one of these groups is a hydrogen atom, then you will get an aldehyde.

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  • An aside: the graphic artist's pixel is a close analog of the scientist's atom.

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  • angstroms from the carbon atom, and making an angle of 120 degrees with the oxygen atom.

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  • If an atom gains an it is called an anion.

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  • aryl halide has a halogen atom attached directly to a benzene ring.

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  • BBC BASIC for the ATOM includes a two-pass assembler using standard 6502 mnemonics.

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  • This might be corrupted data, or a legitimate description of a highly ionized atom.

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  • ionized An atom has the same number of protons and electrons.

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  • Ionization The process by which a neutral atom or molecule acquires or loses an electric charge.

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  • You need to look for a hydrogen atom covalently bonded to a highly electronegative atom, usually nitrogen, oxygen or fluorine.

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  • As the silicon crystal grows oxygen is incorporated as an interstitial atom in the silicon matrix at a concentration of typically 10-40 ppm.

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  • atom bomb.

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  • atom interferometer based on this cooling process.

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  • The nucleus of a hydrogen atom is a proton.

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  • The reaction is a substitution reaction; a hydrogen atom of methane is swapped for a chlorine atom.

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  • Silicon being a larger atom than carbon can form only a single covalent bond with an oxygen atom.

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  • Why does the carbon atom have a positive charge?

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  • The typical helium atom consists of a nucleus of two protons and two neutrons surrounded by two electrons.

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  • A molecule of water (H20) consists of two atoms of hydrogen and one atoms of hydrogen and one atom of oxygen.

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  • Desperate measures were used to conclude the long lasting and cruel war and the decision was made to drop the atom bomb at Hiroshima.

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  • Some observers 3 maintain that India could have produced an atom bomb before China, had it wished so to do.

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  • atom bomb tests in the 1940s.

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  • atomic orbitals: 6 g For any atom, there are nine 6 g orbitals.

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  • occasions Bennett explains of the order atom by j the subject had.

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  • It intends to use the method on 300,000 gallons of liquid waste from atom bomb tests in the 1940s.

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  • bromine atom is being replaced by an OH group in an organic compound.

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  • caesiumecond is now defined by nine billions beats of a cesium atom.

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  • carboxylate CD atom.

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  • Gazing with the eye of God, he will perceive within every atom a door that leadeth him to the stations of absolute certitude.

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  • cesium atom was in use in atomic clocks.

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  • There, the chlorine released by CFCs destroys the ozone at the rate of 100,000 molecules of ozone per chlorine released by CFCs destroys the ozone at the rate of 100,000 molecules of ozone per chlorine atom.

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  • At high collision energies, all protonated benzodiazepines eliminate a hydrogen atom by simple bond cleavage.

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  • coarctate atom, each ring appears to sustain aromaticity associated with its own 4n or 4n+2 p -electron count.

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  • complementarity of shape and of atom types (chemistry) are common features of good protein-ligand binding.

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  • Europe - you stifled the voice of God, and so you invented the concentration camp and the Atom Bomb.

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  • crystallized form of the protein, a three-dimensional image â precise down to the atom â was obtained.

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  • The program should return the type of local structure (face centered cubic, etc.) for each atom of the system.

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  • density matrix, array of atom charges (empty on input ).

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  • depends upon the types of atom in the molecule and the way they are arranged.

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  • dodge old - he's got no stomach for running around Siberia dodging atom bombs!

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  • Every cell and atom of the body is a small magnetic dynamo.

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  • dysprosium atom (element 62, abbreviated Dy )?

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  • A free radical is an atom or compound which contains an unpaired electron.

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  • electronegative oxygen atom is considered to gain both pairs of the bonding electrons with hydrogen.

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  • ellipsoid plots containing custom atom colors became truncated during on-screen rotation.

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  • excited atom or molecule to emit a photon?

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  • Quot brand of placing fluorescent the atom by ultra violet.

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  • fluorine atom has 3 very active lone pairs of electrons.

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  • formalism of quantum mechanics for bound systems, in particular, the simple harmonic oscillator and the hydrogen atom.

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  • An aryl halide has a halogen atom attached directly to a benzene ring.

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  • helium atom beam is directed at a sample crystal.

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  • heme group (side view) showing Iron Atom.

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  • hydride ion is a hydrogen atom with an extra electron - hence the lone pair.

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  • Structure 69C has a vertex atom missing from the underlying Mackay icosahedron like 38A.

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  • Suppose you had a single hydrogen atom and at a particular instant plotted the position of the one electron.

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  • Chu has devised an atom interferometer based on this cooling process.

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  • This can be seen in the following picture, in which there is an atom in a tetrahedral interstice.

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  • intramolecular hydrogen atom transfer in cations.

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  • ionized atom.

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  • I don't need jackhammers and atom bomb to get in when I can walk through the door.

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  • jigglean manipulate an atom and we can move an atom around but a few atoms jiggling about is not much good for society.

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  • The routine calculates the square symmetric matrix of distances between each atom and every other atom currently selected.

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  • In the ATOM this is a 6502, a processor designed in 1975 and the best-selling 8-bit microprocessor in 1979.

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  • ATOM ' O ' ' HOH ' extended water mol Type 95.

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  • The SI base unit for concentration is the mol, from which atom fraction and mol fraction are derived.

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  • mol% metal there remains only around 0.7 hydrogen bond per nitrogen atom.

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  • monatomic molecules - molecules of noble gases, like helium, which consist of a single atom.

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  • neutrons in the nucleus of an atom.

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  • nucleus of a hydrogen atom is a proton.

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  • The residual atom (sometimes referred to as the politically incorrect ' daughter nuclide ' !

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  • Even more complicated integrated atom optics devices and networks, similar to integrated circuits for electrons, can be devised.

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  • oxygen atom is readily available to cause oxidation, making it an active compound useful for producing blond hair.

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  • The camphor molecule has one polar atom (a carbonyl oxygen) and three methyl groups.

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  • The lone pairs on the halogen atom interact with the delocalized Pi system, which strengthens the C-X covalent bond.

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  • Each of the four compass points around the atom symbol in a Lewis diagram represents one of the four possible positions for electron pairs.

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  • What causes an excited atom or molecule to emit a photon?

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  • positron emitted from the nucleus of an atom during radioactive decay.

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  • protons in the nucleus of an atom.

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  • protons in an atom gives the atom its atomic number.

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  • Removed pointless and time wasting MAD single additional atom refinement (this may need to be done for MIR too ).

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  • Next, a policeman manning an isolated roadblock tries to confirm rumors of an impending atom bomb attack from increasingly panicked motorists.

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  • undo the two screws which secure the bottom of the Atom.

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  • He's scarily clever and doing his phd on data archiving for the folk at CERN who build atom smashers... .

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  • solute atom or vacancy.

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  • spare a thought for Geordie exile the mighty atom Lorna, her back went mid way during the L & D set.

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  • split the game atom back in '98.

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  • And social atom behavior for the most part lacks spontaneity.

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  • He claimed that Julius had given atom bomb secrets that he in turn passed to Harry Gold, a convicted Soviet spy.

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  • subatomic particle which circles the nucleus of the atom in a cloud.

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  • substitution reaction; a hydrogen atom of methane is swapped for a chlorine atom.

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  • subtended at the atom center tends toward linearity for proton and tetrahedrality for the oxygen transfer.

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  • The crystal symmetry will be used to generate atom positions from a unique molecule.

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  • teleportation of the quantum state of an atom.

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  • The atom we are interested in will therefore tend to carry either a partial positive charge or form a positive ion.

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  • When refining TLS parameters there is a list of the refined TLS groups with the derived anisotropic tensor for each atom in the group.

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  • tertiary halogenoalkanes You would need to keep the halogen atom constant.

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  • This is truly therapeutic because it brings about social atom repair.

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  • spare a thought for Geordie exile the mighty atom Lorna, her back went mid way during the L & D set.

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  • trigonal planar arrangement around the central atom X- .

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  • All of these methods are sensitive to the outermost atom layers at the surface and operate in ultrahigh vacuum.

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  • ATOM (Gr.

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  • (r 810), are reproduced here, in which gases are represented as composed of atoms. Knowing that the gas which he called "nitrous gas" was composed of oxygen and nitrogen, and believing it to be the simplest compound of these two elements, he naturally represented its atom as formed of an atom of oxygen and an atom of nitrogen in juxtaposition.

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  • When two elements form more than one compound, as is the case with oxygen and carbon, he assigned to the compound which he thought the more complex an atom made up of two atoms of the one element and one atom of the other; the diagram for carbonic acid illustrates this, and an extension of the same plan enabled him to represent any compound, however complex its structure.

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  • 00 O (DOG The diagrams show that Dalton formed a very definite conception of the nature of chemical combination; it was the union of a small number of atoms of one kind with a small number of another kind to form a compound atom, or as we now say a "molecule," this identical process being repeated millions of times to form a perceptible amount of a compound.

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  • If we accept the hypothesis that each kind of atom has a specific and invariable weight, we can, with the aid of the above theory, make most important inferences concerning the proportions by weight in which substances combine to form compounds.

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  • Thus if Dalton's diagram for the molecule, propor- or compound atom, of water be correct, it follows that in all samples of water the total number of the hydrogen atoms is equal to that of the oxygen atoms; consequently, the ratio of the weight of oxygen to that of hydrogen in water is the same as the ratio of the weights of an oxygen and a hydrogen atom, and this is invariable.

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  • Modern researches (see Radioactivity) on the complex nature of the atom have a little shaken the belief in the absolute permanence of matter.

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  • To take the simplest possible case, if Dalton had been correct in assuming that the molecule of water was made up of one atom of oxygen and one of hydrogen, then the experimental fact that water contains eight parts by weight of oxygen to one part of hydrogen, would at once show that the atom of oxygen is eight times as heavy as the atom of hydrogen, or that, taking the atomic weight of hydrogen as the unit, the.

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  • Thus the symbol or formula H 2 O for water expresses the view that the molecule of water consists of one atom of oxygen and two of hydrogen; and if we know the atomic weights of oxygen and hydrogen, it also tells us the composition of water by weight.

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  • Dalton believed that the molecules of the elementary gases consisted each of one atom; his diagram for hydrogen gas makes the point clear.

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  • But modern discoveries in radioactivity 2 are in favour of the existence of the atom, although they lead to the belief that the atom is not so eternal and unchangeable a thing as Dalton and his predecessors imagined, and in fact, that the atom itself may be subject to that eternal law of growth and decay of which Lucretius speaks.

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  • By the action of bromine and alcoholic potash on the amides,, they are converted into amines containing one carbon atom less than the original amide, a reaction which possesses great.

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  • It was against them that was broken his invincible will, sweeping away in the defeat the work of Panama, his own fortune, his fame and almost an atom of his honour.

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  • But this atom, only grazed by calumny, has already been restored to him by posterity, for he died poor, having been the first to suffer by the disaster to his illusions.

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  • So far back as 1850 he also suggested a view which, in a modified form, is of fundamental importance in the modern theory of ionic dissociation, for, in a paper on the theory of the formation of ether, he urged that in an aggregate of molecules of any compound there is an exchange constantly going on between the elements which are contained in it; for instance, in hydrochloric acid each atom of hydrogen does not remain quietly in juxtaposition with the atom of chlorine with which it first united, but changes places with other atoms of hydrogen.

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  • The evolution of the notion of elements is treated under Element; the molecular hypothesis of matter under Molecule; and the genesis of, and deductions from, the atomic theory of Dalton receive detailed analysis in the article Atom.

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  • He laid down the following arbitrary rules for determining the number of atoms in a compound: - if only one compound of two elements exists, it is a binary compound and its atom is composed of one atom of each element; if two compounds exist one is binary (say A + B) and the other ternary (say A + 2B); if three, then one is binary and the others may be ternary (A ± 2B, and 2A + B), and so on.

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  • From analyses of water, which he regarded as composed of one atom of hydrogen and one of oxygen, he This dictum was questioned by the researches of H.

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  • deduced the relative weight of the oxygen atom to be 6.5; from marsh gas and olefiant gas he deduced carbon = 5, there being one atom of carbon and two of hydrogen in the former and one atom of hydrogen to one of carbon in the latter; nitrogen had an equivalent of 5, and so on.'

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  • An immediate inference was that the Daltonian " atom " must have parts which enter into combination with parts of other atoms; in other words, there must exist two orders of particles, viz.

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  • Notwithstanding Avogadro's perspicuous investigation, and a similar exposition of the atom and molecule by A.

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  • Torbern Olof Bergman used an elaborate system in his Opuscula physica et chemica (1783); the 1 Dalton's atomic theory is treated in more detail in the article Atom.

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  • 2 Berzelius, however, appreciated the necessity of differentiating the atom and the molecule, and even urged Dalton to amend his doctrine, but without success.

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  • A great advance was made by Dalton, who, besides introducing simpler symbols, regarded the symbol as representing not only the element or compound but also one atom of that element or compound; in other words, his symbol denoted equivalent weights.4 This system, which permitted the correct representation of molecular composition, was adopted by Berzelius in 1814, who, having replaced the geometric signs of Dalton by the initial letter (or letters) of the Latin names of the elements, represented a compound by placing a plus sign between the symbols of its components, and the number of atoms of each component (except in the case of only one atom) by placing Arabic numerals before the symbols; for example, copper oxide was Cu +0, sulphur trioxide S+30.

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  • letters traversed by a horizontal bar, to denote the double atom (or molecule).

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  • He recognized that if an elementary atom had parts, his theory demanded that these parts should carry different electric charges when they entered into reaction, and the products of the reaction should vary according as a positive or negative atom entered into combination.

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  • For instance if the reaction 2112+02=1120+1120 be true, the molecules of water should be different, for a negative oxygen atom would combine in one case, and a positive oxygen atom in the other.

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  • Simultaneously with this discussion of the atom and molecule, great controversy was ranging over the constitution of com pounds, more particularly over the carbon or organic compounds.

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  • They assumed the atom to be the smallest part of matter which can exist in combination, and the molecule to be the smallest part which can enter into a chemical reaction.

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  • In 1860 there prevailed such a confusion of hypotheses as to the atom and molecule that a conference was held at Karlsruhe to discuss the situation.

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  • He chose as his unit of reference the weight of an atom of hydrogen, i.e.

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  • He called this proportion the " atom," since it invariably enters compounds without division, and the weight of this atom is the atomic weight.

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  • Frankland showed that any particular element preferentially combined with a definite number (which might vary between certain limits) of other atoms; for example, some atoms always combined with one atom of oxygen, some with two, while with others two atoms entered into combination with one of oxygen.

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  • If an element or radical combined with one atom of hydrogen, it was termed monovalent; if with two (or with one atom of oxygen, which is equivalent to two atoms of hydrogen) it was divalent, and so on.

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  • The development of the atomic theory and its concomitants - the laws of chemical combination and the notion of atoms and equivalents - at the hands of Dalton and Berzelius, the extension to the modern theory of the atom and molecule, and to atomic and molecular weights by Avogadro, Ampere, Dumas, Laurent, Gerhardt, Cannizzaro and others, have been noted.

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  • A molecule may be defined as the smallest part of a substance which can exist alone; an atom as the smallest part of a substance which can exist in combination.

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  • Thus, the letter H always stands for 1 atom or part by weight of hydrogen, the letter N for 1 atom or 14 parts of nitrogen, and the symbol Cl for 1 atom or 35'5 parts of chlorine.'

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  • Compounds are in like manner represented by writing the symbols of their constituent elements side by side, and if more than one atom of each element be present, the number is indicated by a numeral placed on the right of the symbol of the element either below or above the line.

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  • Thus, hydrochloric acid is represented by the formula HC1, that is to say, it is a compound of an atom of hydrogen with an atom of chlorine, or of i part by weight of hydrogen with 35'5 parts by weight of chlorine; again, sulphuric acid is represented by the formula H 2 SO 4, which is a statement that it consists of 2 atoms of hydrogen, 1 of sulphur, and 4 of oxygen, and consequently of certain relative weights of these elements.

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  • Usually, when the symbols of the elements are written or printed with a figure to the right, it is understood that this indicates a molecule of the element, the symbol alone representing an atom.

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  • In all cases it is usual to represent substances by formulae which to the best of our knowledge express their molecular composition in the state of gas, and not merely the relative number of atoms which they contain; thus, acetic acid consists of carbon, hydrogen and oxygen in the proportion of one atom of carbon, two of hydrogen, and one of oxygen, but its molecular weight corresponds to the formula C211402, which therefore is always employed to represent acetic acid.

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  • It is found that the number of atoms of a given element, of chlorine, for example, which unite with an atom of each of the other elements is very variable.

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  • Thus, hydrogen unites with but a single atom of chlorine, zinc with two, boron with three, silicon with four, phosphorus with five and tungsten with six.

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  • Those elements which are equivalent in combining or displacing power to a single atom of hydrogen are said to be univalent or monad elements; whilst those which are equivalent to two atoms of hydrogen are termed bivalent or dyad elements; and those equivalent to three, four, five or six atoms of hydrogen triad, tetrad, pentad or hexad elements.

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  • For example, in phosphorus pentachloride the five units of affinity possessed by the phosphorus atom are satisfied by the five monad atoms of chlorine, but in the trichloride two are disengaged, and, it may be supposed, satisfy each other.

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  • Thus, it must be supposed that in nitric oxide, NO, an odd number of affinities are disengaged, since a single atom of dyad oxygen is united with a single atom of nitrogen, which in all its compounds with other elements acts either as a triad or pentad.

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  • The oxide NO 2 must be regarded as another instance of a compound in which an odd number of affinities of one of the contained elements are disengaged, since it contains two atoms of dyad oxygen united with a single atom of triad or pentad nitrogen.

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  • Thus, an atom of iodine only combines with one of hydrogen, VI.

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  • 2 a but may unite with three of chlorine, which never combines with more than a single atom of hydrogen; an atom of phosphorus unites with only three atoms of hydrogen, but with five of chlorine, or with four of hydrogen and one of iodine; and the chlorides corresponding to the higher oxides of lead, nickel, manganese and arsenic, Pb0 2, Ni 2 0 3, Mn0 2 and As 2 0 5 do not exist as stable compounds, but the lower chlorides, PbCl 2j NiC12, MnC1 2 and AsC1 3j are very stable.

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  • - Graphic or constitutional formulae are employed to express the manner in which the constituent atoms of compounds are associated together; for example, the trioxide of sulphur is usually regarded as a compound of an atom of hexad sulphur with three atoms of dyad oxygen, and this hypothesis is illustrated by the graphic formula 0=S`O.

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  • In this compound only two of the oxygen atoms are wholly associated with the sulphur atom, each of the remaining oxygen atoms being united by one of its affinities to the sulphur atoms, and by the remaining affinity to an atom of hydrogen; thus H O S ?O H O> The graphic formula of a sulphate is readily deduced by remembering that the hydrogen atoms are partially or entirely replaced.

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  • H O H serves in a measure to express this, three of the atoms of hydrogen being represented as associated with one of the atoms of carbon, whilst the fourth atom is associated with an atom of oxygen which is united by a single affinity to the second atom of carbon, to which, however, the second atom of oxygen is united by both of its affinities.

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  • Each of these OH groups is equivalent in combining or displacing power to a monad element, since it consists of an atom of dyad oxygen associated with a single atom of monad hydrogen, so that in this case the S02 group is equivalent to an atom of a dyad element.

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  • This formula for sulphuric acid, however, merely represents such facts as that it is possible to displace an atom of hydrogen and an atom of oxygen in sulphuric acid by a single atom of chlorine, thus forming the compound SO 3 HC1; and that by the action of water on the compound SO 2 C1 2 twice the group OH, or water minus an atom of hydrogen, is introduced in place of the two monad atoms of chlorine S0 2 C1 2 +2HOH = S0 2 (OH) 2 +2HC1.

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  • Thus, the atom of hydrogen is a monad simple radical, the atom of oxygen a dyad simple radical, whilst the group OH is a monad compound radical.

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  • Dumas gave especial attention to such substitutions, named metalepsy (µeraXntks, exchange); and framed the following empirical laws to explain the reactions: - (1) a body containing hydrogen when substituted by a halogen loses one atom of hydrogen for every atom of halogen introduced; (2) the same holds if oxygen be present, except that when the oxygen is present as water the latter first loses its hydrogen without replacement, and then substitution according to (1) ensues.

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  • The recognition of the polybasicity of acids, which followed from the researches of Thomas Graham and Liebig, had caused Williamson to suggest that dibasic acids could be referred to a double water type, the acid radical replacing an atom of hydrogen in each water molecule; while his discovery of tribasic formic ether, CH(OC 2 H 5) 3, in 1854 suggested a triple water type.

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  • Pointing out that condensed types can only be fused with a radical replacing more than one atom of hydrogen, he laid the foundation of the doctrine of valency, a doctrine of incalcul able service to the knowledge of the structure of chemical compounds.

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  • By its aid the molecule is represented as a collection of atoms connected together by valencies in such a manner that the part played by each atom is represented;.

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  • Gomberg's triphenyl-methyl play no part in what follows), it is readily seen that the simplest hydrocarbon has the formula CH 4, named methane, in which the hydrogen atoms are of equal value, and which may be pictured as placed at the vertices of a tetrahedron, the carbon atom occupying the centre.

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  • E., C being a carbon atom and A.B.D.

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  • Chem., 1888, 2, p. 553), who prepared the four nitromethanes, CH 3 N 2 0, each atom in methane being successively replaced by the nitro-group.

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  • This readily gave with silver nitrite a nitromethane in which we may suppose the nitro-group to replace the a hydrogen atom, i.e.

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  • Chlorination of this substance gave a monochloracetic acid; we will assume the chlorine atom to replace the b hydrogen atom.

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  • From the nitroacetic acid obtained above, malonic acid was prepared, and from this a monochlormalonic acid was obtained; we assume the chlorine atom to replace the c hydrogen atom.

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  • This compound may be considered as derived from methane, CH 4, by replacing a hydrogen atom by the monovalent group CH 3, known as methyl; hence ethane may be named " methylmethane."

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  • It is obvious that we have derived three combinations of carbon with hydrogen, characterized by containing a single, double, and triple linkage; and from each of these, by the substitution of a methyl group for a hydrogen atom, compounds of the same nature result.

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  • Equally well we may derive it from methane by replacing a hydrogen atom by the monovalent group CH 2 CH 31 named ethyl; hence propane may be considered as " ethylmethane."

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  • Further, since methane may be regarded as formed b y the conjunction of a methyl group with a hydrogen atom, it may be named " methyl hydride "; similarly ethane is " ethyl hydride," propane, " propyl hydride," and so on.

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  • In propane, on the other hand, the hydrogen atoms attached to the terminal carbon atoms differ from those joined to the medial atom; we may therefore expect to obtain different compounds according to the position of the hydrogen atom substituted.

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  • CH3, known as " normal " or n-butane, substitution occurring at a terminal atom, or CH 3.

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  • CH(CH 3) CH 3, isobutane, substitution occurring at the medial atom.

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  • (methylene) groups and the molecule consists of a single chain; such hydrocarbons are referred to as being normal; (2) has a branch and contains the group; CH (methine) in which the free valencies are attached to carbon atoms; such hydrocarbons are termed secondary or iso-; (3) is characterized by a carbon atom linked directly to four other carbon atoms; such hydrocarbons are known as tertiary.

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  • It will be seen that each type depends upon a specific radical or atom, and the copulation of this character with any hydrocarbon radical (open or cyclic) gives origin to a compound of the same class.

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  • Thus from ethyl alcohol there can be prepared compounds, termed esters, or ethereal salts, exactly comparable in structure with corresponding salts of, say, potassium; by the action of the phosphorus haloids, the hydroxyl group is replaced by a halogen atom with the formation of derivatives of the type R Cl(Br,I); nitric acid forms nitrates, R O NO 2; nitrous acid, nitrites, R O NO; sulphuric acid gives normal sulphates R 2 SO 4, or acid sulphates, R SO 4 H.

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  • An important class of compounds, termed amines (q.v.), results from the condensation of alcohols with ammonia, water being eliminated between the alcoholic hydroxyl group and a hydrogen atom of the ammonia.

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  • Assuming the four valencies of the carbon atom to be directed from the centre of a regular tetrahedron towards its four corners, the angle at which they meet.

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  • As an illustration it may be pointed out that in the case of the two known types of lactones - the y-lactones, which contain four carbon atoms and one oxygen atom in the ring, are more readily formed and more stable (less readily hydrolysed) than the S-lactones, which contain one oxygen and five carbon atoms in the ring.

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  • The ringed structure of benzene, C 6 H 61 was first suggested in 1865 by August Kekule, who represented the molecule by six CH groups placed at the six angles of a regular hexagon, the sides of which denoted the valencies saturated by adjacent carbon atoms, the fourth valencies of each carbon atom being represented as saturated along alternate sides.

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  • This symbol is in general use; it is assumed that at each corner there is a CH group which, however, is not always written in; if a hydrogen atom be substituted by another group, then this group is attached to the corner previously occupied by the displaced hydrogen.

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  • a carbon atom which is united to other carbon atoms by its remaining three valencies; hence on oxidation they cannot yield the corresponding aldehydes, ketones or acids (see below, Decompositions of the Benzene Ring).

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  • The amines also exhibit striking differences: in the aliphatic series these compounds may be directly formed from the alkyl haloids and ammonia, but in the benzene series this reaction is quite impossible unless the haloid atom be weakened by the presence of other substituents, e.g.

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  • that two pairs of hydrogen atoms are symmetrically situated with reference to any specified hydrogen atom, the absolute demonstration of the validity of OH these assumptions was first given by A.

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  • These results may be graphically represented as follows: numbering the hydrogen atoms in cyclical order from i to 6, then the first thesis demands that whichever atom is substituted the same compound results, while the second thesis points out that the pairs 2 and 6, and 3 and 5 are symmetrical with respect to 1, or in other words, the di-substitution derivatives 1.2 and 1.6, and also 1.3 and 1.5 are identical.

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  • The proof is divided into two parts: (1) that four hydrogen atoms are equal, and (2) that two pairs of hydrogen atoms are symmetrical with reference to a specified hydrogen atom.

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  • From meta-brombenzoicacid two nitrobrombenzoic ac i ds are obtained on direct nitration; elimination of the bromine atom and the reduction of the nitro to an amino group in these two acids results in the formation of the same ortho-aminobenzoic acid.

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  • Intermolecular transformations-migrations of substituent groups from one carbon atom to anotherare of fairly common occurrence among oxy compounds at elevated temperatures.

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  • Arguing from the existence of only one mono-substitution derivative, and of three di-derivatives (statements of which the rigorous proof was then wanting), he was led to arrange the six carbon atoms in a ring, attaching a hydrogen atom to each carbon atom; being left with the fourth carbon valencies, he mutually saturated these in pairs, thus obtaining the symbol I (see below).

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  • He assumed that if we have one atom 1 It is now established that ortho compounds do exist in isomeric forms, instances being provided by chlor-, brom-, and amino-toluene, chlorphenol, and chloraniline; but arguments, e.g.

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  • Now suppose two of the attached atoms are replaced by one atom, then this atom must have two valencies directed to the central atom; and consequently, in the same unit of time, the central atom will collide once with each of the two monovalent atoms and twice with the divalent.

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  • Applying this notion to benzene, let us consider the impacts made by the carbon atom (I) which we will assume to be doubly linked to the carbon atom (2) and singly linked to (6), h standing for the hydrogen atom.

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  • This implied that in the benzene complex there was at least one carbon atom linked to three others, thus rendering Kekule's formula impossible and Ladenburg's and Claus' possible.

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  • Succinosuccinic ester behaves both as a ketone and as a phenol, thereby exhibiting desmotropy; assuming the ketone formula as indicating the constitution, then in Baeyer's equation we have a migration of a hydrogen atom, whereas to bring Ladenburg's formula into line, an oxygen atom must migrate.

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  • Thiele suggested a doctrine of " partial valencies," which assumes that in addition to the ordinary valencies, each doubly linked atom has a partial valency, by which the atom first interacts.

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  • (The stereo-chemistry of carbon compounds has led to the spatial representation of a carbon atom as being situated at the centre of a tetrahedron, the four valencies being directed towards the apices; see above, and Isomerism.) A form based on Kekule's formula consists in taking three pairs of tetrahedra, each pair having a side in common, and joining them up along the sides of a regular hexagon by means of their apices.

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  • Zeit., 1905, 29, p. 30), assumed the six carbon atoms to occupy six of the corners of a cube, each carbon atom being linked to a hydrogen atom and by single bonds to two neighbouring carbon atoms, the remaining valencies being directed to the unoccupied corners of the cube, three to each, where they are supposed to satisfy each other.

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  • The formula has the advantage that it may be constructed from tetrahedral models of the carbon atom; but it involves the assumption that the molecule has within it a mechanism, equivalent in a measure to a system of railway points, which can readily close up and pass into that characteristic of benzene.

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  • Similarly a CH group may be replaced by a nitrogen atom with the production of compounds of similar stability; thus benzene gives pyridine, naphthalene gives quinoline and isoquinoline; anthracene gives acridine and a and 3 anthrapyridines.

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  • The transition between the two classes as differentiated above may be illustrated by the following cyclic compounds, each of which contains a ring composed of four carbon atoms and one oxygen atom: CH CH/ CH CH/ CH CO I CH CO' CH =CH c Tetramethylene But yrolactone.

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  • Six-membered ring systems can be referred back, in a manner similar to the above, to pyrone, penthiophene and pyridine, the substances containing a ring of five carbon atoms, and an oxygen, sulphur and nitrogen atom respectively.

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  • If, however, two compounds only differ with regard to the spatial arrangement of the atoms, the physical properties may be (I) for the most part identical, differences, however, being apparent with regard to the action of the molecules on polarized light, as is the case when the configuration is due to the presence of an asymmetric atom (optical isomerism); or (2) both chemical and physical properties may be different when the configuration is determined by the disposition of the atoms or groups attached to a pair of doubly-linked atoms, or to two members of a ring system (geometrical isomerism or allo-isomerism).

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  • the amount which is equivalent to one part of hydrogen; and (2) a factor which denotes the number of atoms of hydrogen which combines with or is equivalent to one atom of the particular element.

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  • The substitution of a hydrogen atom by the hydroxyl group generally occasions a rise in boiling-point at about Ioo°.

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  • Soc., 18 93, 6 3, p. 465) states, that the melting-point of any odd member of a homologous series is lower than the melting-point of the even member containing one carbon atom less.

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  • The identity of the four valencies of the carbon atom follows from the fact that the heats of combustion of methane, ethane, propane, trimethyl methane, and tetramethyl methane, have a constant difference in the order given, viz.

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  • 158.6 calories; this means that the replacement of a hydrogen atom by a methyl group is attended by a constant increase in the heat of combustion.

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  • If twelve grammes of amorphous carbon be burnt to carbon dioxide under constant volume, the heat evolved (96.96 cal.) does not measure the entire thermal effect, but the difference between this and the heat required to break down the carbon molecule into atoms. If the number of atoms in the carbon molecule be denoted by n, and the heat required to split off each atom from the molecule by d, then the total heat required to break down a carbon molecule completely into atoms is nd.

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  • Theabsolute heat of combustion of a carbon atom is therefore 135.34 calories, and this is independent of the form of the carbon burned.

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  • We assume that each carbon atom and each hydrogen atom contributes equally to the thermal effect.

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  • If a be the heat evolved by each carbon atom, and # that by each hydrogen atom, the thermal effect may be expressed as H =na+2m/ - A, where A is the heat required to break the molecule into itsconstituent atoms. If the hydrocarbon be saturated, i.e.

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  • It is remarkable that the difference in the heats of formation of ketones and the paraffin containing one carbon atom less is 67.94 calories, which is the heat of formation of carbon monoxide at constant volume.

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  • Thus oxygen varies according as whether it is linked to hydrogen (hydroxylic oxygen), to two atoms of carbon (ether oxygen), or to one carbon atom (carbonyl oxygen); similarly, carbon varies according as whether it is singly, doubly, or trebly bound to carbon atoms.

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  • Baeyer has suggested that the nine carbon atom system of xanthone may act as a chromophore.

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  • An alternative view, due to Green, is that the oxygen atom of the xanthone ring is tetravalent, a supposition which permits the formulation of these substances as ortho-quinonoids.

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  • The chlorine atom in this compound is replaced by the cyano-group, which is then reduced to the CH 2 NH 2.

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  • Beckmann, Ber., 1886, 1 9, p. 9 8 9; 188 7, 20, p. 2580), yielding as final products an acid-amide or anilide, thus: RC(:N OH)R'-RC(OH) :NR' ---> As regards the constitution of the oximes, two possibilities exist, namely >C: NOH, or > C' ?, and the first of these is presumably correct, since on alkylation and subsequent hydrolysis an alkyl hydroxylamine of the type NH 2 OR is obtained, and consequently it is to be presumed that in the alkylated oxime, the alkyl group is attached to oxygen, and the oxime itself therefore contains the hydroxyl group. It is to be noted that the oximes of aromatic aldehydes and of unsymmetrical aromatic ketones frequently exist in isomeric forms. This isomerism is explained by the HantzschWerner hypothesis (Ber., 1890, 23, p. II) in which the assumption is made that the three valencies of the nitrogen atom do not lie in the same plane.

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  • , the former, N OH HO N where the H atom and OH group are contiguous, being known as syn-aldoximes and the latter as the anti-aldoximes.

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  • -> CH3C6H5CONHC6H51 N OH Syn-phenyltolylketoxime CH3 C6H4 C C6H5 CH3C6H4NH000,H5 HO N A nti-tolylphenylketoxime In the case of the aldoximes, that one which most readily loses the elements of water on dehydration is assumed to contain its hydroxyl radical adjacent to the movable hydrogen atom and is designated the syn-compound.

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  • Here the ions are potassium and the group Ag(CN)2.1 Each potassium ion as it reaches the cathode precipitates silver by reacting with the solution in accordance with the chemical equation K--+KAg(CN) 2 =2KCN+Ag, while the anion Ag(CN) 2 dissolves an atom of silver from the anode, and re-forms the complex cyanide KAg(CN) 2 by combining with the 2KCN produced in the reaction described in the equation.

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  • Thomson has shown (see CONDUCTION, ELECTRIC, § III.) that the negative ions in certain cases of gaseous conduction are much more mobile than the corresponding positive ions, and possess a mass of about the one-thousandth part of that of a hydrogen atom.

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  • In gases the electrons sometimes travel alone, but in liquids they are always attached to matter, and their motion involves the movement of chemical atoms or groups of atoms. An atom with an extra corpuscle is a univalent negative ion, an atom with one corpuscle detached is a univalent positive ion.

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  • In metals the electrons can slip from one atom to the next, since a current can pass without chemical action.

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  • When a current passes from an electrolyte to a metal, the electron must be detached from the atom it was accompanying and chemical action be manifested at the electrode.

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  • The aldehyde group reacts with hydrocyanic acid to produce two stereo-isomeric cyanhydrins; this isomerism is due to the conversion of an originally non-asymmetric carbon atom into an asymmetric one.

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  • Since the molecule contains an asymmetric carbon atom, the acid exists in three forms, one being an inactive "racemic" mixture, and the other two being optically active forms. The inactive variety is known as paramandelic acid.

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  • The mass of each is about 3 7 1 o T th part of that of a hydrogen atom, and with each is indissolubly associated a charge of negative electricity equal to about 3.1 Xio '° C.G.S.

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  • An electrically neutral atom is believed to be constituted in part, or perhaps entirely, of a definite number of electrons in rapid motion within a " sphere of uniform positive electrification " not yet explained.

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  • One or more of the electrons may be detached from the system by a finite force, the number so detachable depending on the valency of the atom; if the atom loses an electron, it becomes positively electrified; if it receives additional electrons, it is negatively electrified.

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  • Whence oM_ HT e, M - 4 71m 1 The charge associated with a corpuscle is the same as that carried by a hydrogen atom.

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  • Mag., 1881, 11, 387) pointed out that this latter constituted the indivisible " atom of electricity " or natural unit charge.

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  • The application of this term to Thomson's corpuscle implies, rightly or wrongly, that notwithstanding its apparent mass, the corpuscle is in fact nothing more than an atom of electricity.

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  • The hydrogen in the primary and secondary nitro compounds which is attached to the same carbon atom as the nitro group is readily replaced by bromine in alkaline solution.

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  • The pseudo-nitrols, RR':C(NO)(NO 2), may be obtained by the action of nitrous acid on the secondary nitroparaffins; by the action of silver nitrite on such bromnitrosoparaffins as contain the bromine and the nitroso group united to the same carbon atom (0.

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  • Piperic acid differs from piperonylic acid by the group C4H 4, and it was apparent that these carbon atoms must be attached to the carbon atom which appears in the carboxyl group of piperonylic acid, for if they were directly attached to the benzene ring polycarboxylic acids would result in oxidation.

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  • Toxins may thus become so closely keyed into their corresponding atom groups, as for instance in tetanus, that they are no longer free to combine with the antitoxin; or, again, an antitoxin injected before a toxin may anticipate it and, preventing its mischievous adhesion, dismiss it for excretion.

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  • Formic acid yields acridine, and the higher homologues give derivatives substituted at the meso carbon atom, N N +[[Hcooh-C 6 H 5 /Inc6h5->C6h4 C6h4 Cho Ch N N +Ch 3 000h->C 6 H 5 /IC 6 H 5 --C 6 H 4 C6h4 Coch 3 C]](CH3) Acridine may also 1:e obtained by passing the vapour of phenylortho-toluidine through a red-hot tube (C. Graebe, Ber., 1884, 17, p. 1 37 0); by condensing diphenylamine with chloroform, in presence of aluminium chloride (0.

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  • The organic derivatives of silicon resemble the corresponding carbon compounds except in so far that the silicon atom is not capable of combining with itself to form a complex chain in the same manner as the carbon atom, the limit at present being a chain of three silicon atoms. Many of the earlier-known silicon alkyl compounds were isolated by Friedel and Crafts and by Ladenburg, the method adopted consisting in the interaction of the zinc alkyl compounds with silicon halides or esters of silicic acids.

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  • Most metals form carbonates (aluminium and chromium are exceptions), the alkali metals yielding both acid and normal carbonates of the types Mhco 3 and M 2 CO 3 (M = one atom of a monovalent metal); whilst bismuth, copper and magnesium appear only to form basic carbonates.

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  • He held the doctrine that the chemical elements are compounds of equal and similar atoms, and might therefore possibly be all derived from one generic atom.

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  • The facts suggested that the six carbon atoms formed a chain, and that a hydroxy group was attached to five of them, for it is very rare for two hydroxy groups to be attached to the same carbon atom.

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  • The remaining oxygen atom is aldehydic or ketonic, for the sugars combine with hydrocyanic acid, hydroxylamine and phenylhydrazine.

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  • - The cyanhydrins on hydrolysis give monocarboxylic acids, which yield lactones; these compounds when reduced by sodium amalgam in sulphuric acid solution yield a sugar containing one more carbon atom.

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  • The identity of the formulae and osazones of d-mannose and d-glucose showed that the stereochemical differences were situated at the carbon atom adjacent to the aldehyde group. Fischer applied a method indicated by Pasteur in converting dextro into laevo-tartaric acid; he found that both d-mannonic and d-gluconic acids (the latter is yielded by glucose on oxidation) were mutually convertible by heating with quinoline under pressure at 140°.

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  • Although containing an asymmetric carbon atom it has not been resolved.

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  • Employing the notation in which the molecule is represented vertically with the aldehyde group at the bottom, and calling a carbon atom+or - according as the hydrogen atom is to the left or right, the possible configurations are shown in the diagram.

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  • When such compounds are converted into corresponding dibasic acids, CO 2 H.[CH(OH)) 3.00 2 H, the number of asymmetric carbon atoms becomes reduced from three to two, as the central carbon atom is then no longer associated with four, but with only three different radicles.

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  • The replacement of one hydrogen atom by one alkyl or aryl group gives rise to primary amines; of two hydrogen atoms by two groups, to secondary amines; of three hydrogen atoms by three groups, to tertiary amines.

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  • If the nitrogen atom in the quaternary ammonium salts be in combination with four different groups, then the molecule is asymmetrical, and the salt can be resolved into optically active enantiamorphous isomerides.

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  • Since the acid contains an asymmetric carbon atom, it can exist in three forms, a dextro-rotatory, a laevo-rotatory and an inactive form; the acid obtained in the various synthetical processes is the inactive form.

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  • Dalton's idea that elements preferentially combined in equiatomic proportions had as an immediate inference that metallic oxides contained one atom of the metal to one atom of oxygen, and a simple expansion of this conception was that one atom of oxide combined with one atom of acid to form one atom of a neutral salt.

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  • A polybasic acid contains more than one atom of hydrogen which is replaceable by metals; moreover, in such an acid the replacement may be entire with the formation of normal salts, partial with the formation of acid salts, or by two or more different metals with the formation of compound salts (see Salts).

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  • OH, termed the carboxyl group, in which the hydrogen atom is replaceable by metals with the formation of salts, and by alkyl radicals with the formation of esters.

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  • Their experiments, although not conclusive, appear to indicate that the molecule of a metal when in dilute solution often consists of one atom.

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  • Sir Edward Frankland,showed how it could be derived from, and converted into, ethane; and thus determined it to be ethane in which one hydrogen atom was replaced by a hydroxyl group. Its constitutional formula is therefore CH3�CH2.OH.

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  • The assumption usually made is that the total kinetic energy of the molecules, including possible energy of rotation or vibration if the molecules consist of more than one atom, is proportional to the energy of translation in the case of an ideal gas.

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  • Rutherford had announced the nuclear theory of atomic structure which required each atom to consist of a minute positively charged nucleus about which negative electrons were distributed.

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  • This number is probably to be identified with the electric charge upon the nucleus of the atom.

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  • The word appears to have been invented during the 17th century, and remained synonymous with " atom " (Gr.

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  • " Atom " has mainly a chemical import, being defined as the smallest particle of matter which can take part in a chemical reaction; a " molecule " is composed of atoms, generally two or more.

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  • For the detailed chemical significance of these terms, see Chemistry; and for the atomic theory of the chemist (as distinguished from the atomic or molecular theory of the physicist) see Atom; reference may also be made to the article Matter.

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  • The leading historical stages in the evolution of the modern conception of the molecular structure of matter are treated in the following passage from James Clerk Maxwell's article Atom in the 9th edition of the Ency.

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  • " Atom 1 (iiTopos) is a body which cannot be cut in two.

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  • " The atomists assert that after a certain number of such divisions the parts would be no longer divisible, because each of them would be an atom.

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  • If it were not so, Lucretius tells us, there could be no motion, for the atom which gives way first must have some empty place to move into.

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  • " The opposite school maintained then, as they have always done, 1 It wiII be noted that Clerk Maxwell's " atom " and " atomic theory " have the significance which we now attach to " molecule " and " molecular theory."

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  • According to Boscovich matter is made up of atoms. Each atom is an indivisible point, having position in space, capable of motion in a continuous path, and possessing a certain mass, whereby a certain amount of force is required to produce a given change of motion.

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  • Besides this the atom is endowed with potential force, that is to say, that any two atoms attract or repel each other with a force depending on their distance apart.

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  • " Thus, in Boscovich's theory, the atom has continuity of existence in time and space.

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  • On the other hand, the atom itself has no parts or dimensions.

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  • So far as is known, each line in the spectrum of, say, mercury, represents a possibility of a distinct vibration of the mercury atom, and accordingly provides two terms (say aq;, 2 +.

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  • Now if the atoms are regarded as points or spherical bodies oscillating about positions of equilibrium, the value of n+3 is precisely six, for we can express the energy of the atom in the form (9 2 v a 2 v a2v E = z(mu 2 +mv 2 +mw 2 +x 2 ax2 + y2ay2-fz2az2), where V is the potential and x, y, z are the displacements of the atom referred to a certain set of orthogonal axes.

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  • The difficulty is further diminished when it is proved, as it can be proved, 2 that the modes of energy represented in the atomic spectrum acquire energy so slowly that the atom might undergo collisions with other atoms for centuries before being set into oscillations which would possess an appreciable amount of energy.

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  • The other course is to consider matter as formed of ultimate atoms, each the nucleus or core of an intrinsic modification impressed on the surrounding region of the aether; this might conceivably be of the nature of vortical motion of a liquid round a ring-core, thus giving a vortex atom, or of an intrinsic strain of some sort radiating from a core, which would give an electric atom.

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  • We recognize an atom only through its physical activities, as manifested in its interactions with other atoms at a distance from it; this field of physical activity would be identical with the surrounding field of aethereal motion or strain that is inseparably associated with the nucleus, and is carried on along with it as it moves.

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  • Here then we have the basis of a view in which there are not two media to be considered, but one medium, homogeneous in essence and differentiated as regards its parts only by the presence of nuclei of intrinsic strain or motion - in which the physical activities of matter are identified with those arising from the atmospheres of modified aether which thus belong to its atoms. As regards laws of general physical interactions, the atom is fully represented by the constitution of this atmosphere, and its nucleus may be left out of our discussions; but in the problems of biology great tracts of invariable correlations have to be dealt with, which seem hopelessly more complex than any known or humanly possible physical scheme.

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  • An important question arises whether, when a material body is moved through the aether, the nucleus of each atom carries some of the surrounding aether along with it; or whether it practically only carries on its strain-form or physical atmosphere, which is transferred from one portion of aether to another after the manner of a shadow, or rather like a loose knot which can slip along a rope without the rope being required to go with it.

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  • A dielectric substance is electrically polarized by a field of electric force, the atomic poles being made up of the displaced positive and negative intrinsic charges in the atom: the polarization per unit volume (f',g',h') may be defined on the analogy of magnetism, and d/dt(f',g',h') thus constitutes true electric current of polarization, i.e.

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  • The establishment and convection of a single polar atom constitutes in fact a quasi-magnetization, in addition to the polarization current as above defined, the negative poles completing the current circuits of the positive ones.

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  • As unsaturated compounds they can combine with two monovalent atoms. Hydrogen is absorbed readily at ordinary temperature in the presence of platinum black, and paraffins are formed; the halogens (chlorine and bromine) combine directly with them, giving dihalogen substituted compounds; the halogen halides to form monohalogen derivatives (hydriodic acid reacts most readily, hydrochloric acid, least); and it is to be noted that the haloid acids attach themselves in such a manner that the halogen atom unites itself to the carbon atom which is in combination with the fewest hydrogen atoms (W.

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  • Sand, Ber., 1900, 33, pp. 1 34 0 et seq.), and those with a tertiary carbon atom yield double salts with zinc chloride.

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  • Chemie, 1867, 3, p. 39), ascribes to the molecule a peroxide configuration which accounts for its oxidizing powers but not for the fact that each oxygen atom is capable of replacement by one atom of chlorine.

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  • " To the naked eye it looked like a little black atom darting about in a most wonderful manner."

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  • - Hydrocyanic acid forms two series of derivatives by the exchange of its hydrogen atom for alkyl or aryl groups; namely the nitriles, of type R CN, and the isonitriles, of type R NC. The latter compounds may be considered as derivatives of the as yet unknown isohydrocyanic acid HNC.

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  • This reaction shows that the alkyl or aryl group is attached to the carbon atom in the nitrile.

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  • This reaction shows that the alkyl or aryl group is linked to the nitrogen atom.

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  • The carbon atom in the isonitriles is assumed by J.

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  • Nef to be divalent, since these substances readily form addition compounds, such addition taking place on the carbon atom, as is shown by the products of hydrolysis; for example with ethyl carbylamine: C 2 H 5 NC -FCH 3 C0C1--> C 2 H 5 NC(00CH 3)CI -->HCI -{- C2H5NH3 -fCH3CO C02H.

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  • Such a reaction can only take place if the addition of the alkyl group takes place on the nitrogen atom of the isonitrile, from which it follows that the nitrogen atom must be trivalent and consequently the carbon atom divalent.

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  • Wade (loc. cit.) explains the formation of nitriles from potassium cyanide, and of isonitriles from silver cyanide by the assumption that unstable addition products are formed, the nature of which depends on the relative state of unsaturation of the carbon and nitrogen atoms under the varying conditions: KNC--KN :C(:C 2 H 5 I) --SKI +C2H5CN, AgNC->AgN(:C2H51)C---AgI-f-C2H5NC; that is, when the metal is highly electro-positive the carbon atom is the more unsaturated, the addition takes place on the carbon atom, and nitriles are produced.

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  • On the other hand, when there is but little electro-chemical difference between the radical of the cyanide and that of the reacting compound then the nitrogen atom is the more unsaturated element and.

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  • Chromium salts readily combine with ammonia to form complex salts in which the ammonia molecule is in direct combination with the chromium atom.

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  • Acid anhydrides replace the imino-hydrogen atom by acidyl radicals, and boiling with water converts them into phenols.

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  • The electrons responsible for the radiation are probably few and not directly involved in the structure of the atom, which according to the view at present in favour, is itself made up of electrons.

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  • As there is undoubtedly a connexion between thermal motion and radiation, the energy of these electrons within the atom must be supposed to increase with temperature.

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  • highest temperatures at our command it is small compared with the energy of translatory motion, but as the temperature increases, it must ultimately gain the upper hand, and if there is anywhere such a temperature as that of several million degrees, the greater part of the total energy of a body will be outside the atom and molecular motion ultimately becomes negligible compared with it.

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  • Considering the complexity of the subject it is not surprising that the efforts to connect theoretically the possible periods of the atom considered as a vibrating system have met with no considerable success.

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  • The one endeavours to determine the conditions, which are consistent with our knowledge of atomic constitution derived from other sources, and lead to systems of vibration similar to those of the actual atom.

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  • Jeans, 2 who showed that a shell-like constitution of the atom, the shells being electrically charged, 1 Proc. Roy.

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  • On the whole it seems probable that the system of moving electrons, which according to a modern theory constitute the atom, is not directly concerned in thermal radiation which would rather be due to a few more loosely connected electrons hanging on to the atom.

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  • The difficulty that a number of spectroscopic lines seem to involve at least an equal number of electrons may be got over by imagining that the atom may present several positions of equilibrium to the electron, which it may occupy in turn.

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  • Such spectra seem to be characteristic of complex molecular structure, as they appear when compounds are raised to incandescence without decomposition, or when we examine the absorption spectra of vapours such as iodine and bromine and other cases where we know that the molecule consists of more than one atom.

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  • At the same time his synechological view prevented him from saying that every atom has a soul, because according to him a soul always corresponds to a unity of a physical manifold.

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  • See Henry, Life of Dalton, Cavendish Society (1854); Angus Smith, Memoir of John Dalton and History of the Atomic Theory (1856), which on pp. 253-263 gives a list of Dalton's publications; and Roscoe and Harden, A New View of the Origin of Dalton's Atomic Theory (1896); also Atom.

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  • Blagden (Ber.,1900,33,p.2544), who consider that three simultaneous reactions occur, namely, the formation of labile double salts which decompose in such a fashion that the radical attached to the copper atom wanders to the aromatic nucleus; a catalytic action, in which nitrogen is eliminated and the acid radical attaches itself to the aromatic nucleus; and finally, the formation of azo compounds.

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  • This change only occurs when the halogen atom is in the orthoor paraposition to the - N2 - group.

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  • Hantzsch, Ber., This assumption also shows the relationship of the diazonium hydroxides to other quaternary ammonium compounds, for most of the quaternary ammonium hydroxides (except such as have the nitrogen atom attached to four saturated hydrocarbon radicals) are unstable, and readily pass over into compounds in which the hydroxyl group is no longer attached to the amine nitrogen; thus the syn-diazo hydroxides are to be regarded as pseudo-diazonium derivatives.

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  • In the case of metamerism we can imagine that the atoms are differently linked, say in the case of butylene that the atoms of carbon are joined together as a continuous chain, expressed by CC C C, normally as it is called, whereas in isobutylene the fourth atom of carbon is not attached to the third but to the second carbon atom, i.e.

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  • The cases of mutual transformation are generally characterized by the fact that in the compound of higher molecular weight no new links of carbon with carbon are introduced, the trioxymethylene being O CH2-0 CH 2 whereas honey-sugar correg probably C C H 2 -0% sponds to CH 2 0H [[Choh Choh Choh Choh Cho]], each point representing a linking of the carbon atom to the next.

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  • As carbon tends to hold the atom attached to it, one may presume that this property expresses itself in a predominant way where the other element is carbon also, and so the linkage represented by -C-C-is one of the most difficult to loosen.

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  • In this case it is readily seen that isomerism introduces itself in the three carbon atom derivative: the propyl alcohols, expressed by the formulae CH 3 CH2 CH 2 0HandCH 3 CHOH CH3, are known as propyl and isopropyl alcohol respectively.

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  • Frankland, when in 1858 Kekule published a paper in which, after giving reasons for regarding carbon as a tetravalent element, he set forth the essential features of his famous doctrine of the linking of atoms. He explained that in substances containing several carbon atoms it must be assumed that some of the affinities of each carbon atom are bound by the affinities of the atoms of other elements contained in the substance, and some by an equal number of the affinities of the other carbon atoms. The simplest case is when two carbon atoms are combined so that one affinity of the one is tied to one affinity of the other; two, therefore, of the affinities of the two atoms are occupied in keeping the two atoms together, and only the remaining six are available for atoms of other elements.

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  • The high conductivity of metals is then explained by the small mass and high velocity of diffusion of these electric atoms. Assuming the kinetic energy of an electric atom at any temperature to be equal to that of a gaseous molecule, its velocity, on Sir J.

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  • VALERIC ACID, or [[Valerianic Acid, C4h9 C02h]], an organic acid belonging to the fatty acid series, which exists in four isomeric forms, one of which contains an asymmetric carbon atom and consequently occurs in two optically active modifications and one optically inactive modification.

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  • Walden point out from the physico-chemical standpoint that in water and hydrogen peroxide the oxygen atom is probably quadrivalent.

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  • A Hypothesis Doubtfully Attributed To Maxwell Is That Each Additional Atom In The Molecule Is Equivalent To Two Extra Degrees Of Freedom.

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  • The Ideal Atomic Heat Is The Thermal Capacity Of A Gramme Atom In The Ideal State Of Monatomic Gas At Constant Volume.

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  • For the so-called "disintegration of the thorium atom" and the relation of this element to the general subject of radio-active emanations, see Radio-Activity.

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  • His vague dualism works a very distinct advance upon the crude hylozoism of the early Ionians (see Atom), and the criticisms of Plato and Aristotle show how highly his work was esteemed.

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  • The imino hydrogen atom is easily replaced by metals.

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  • about drcith part of the mass of a hydrogen atom."

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  • The subject was pursued by Thomson and the Cambridge physicists with great mathematical and experimental ability, and finally the conclusion was reached that in a high vacuum tube the electric charge is carried by particles which have a mass only a fraction, as above mentioned, of that of the hydrogen atom, but which carry a charge equal to the unit electric charge of the hydrogen ion as found by electrochemical researches.

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  • 2 Later results show that the mass of a hydrogen atom is not far from I.

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  • The diameter of a chemical atom is of the order of z07 centimetre.

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  • The final outcome of these investigations was the hypothesis that Thomson's corpuscles or particles composing the cathode discharge in a high vacuum tube must be looked upon as the ultimate constituent of what we call negative electricity; in other words, they are atoms of negative electricity, possessing, however, inertia, and these negative electrons are components at any rate of the chemical atom.

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  • For the hydrogen atom the ratio of charge to mass as deduced from electrolysis is about Io 1.

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  • Hence the mass of an electron is y ff l iT uth of that of a hydrogen atom.

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  • Trans., 1894, 185; 1895, 186; 1897, 190), and subsequently in his book Aether and Matter (1900), a remarkable hypothesis of the structure of the electron or corpuscle, which he regards as simply a strain centre in the aether or electromagnetic medium, a chemical atom being a collection of positive and negative electrons or strain centres in stable orbital motion round their common centre of mass (see Aether).

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