Thus, the symbols 14 2 and P4 indicate that the molecules of hydrogen and phosphorus respectively contain 2 and 4 atoms. Since, according to the molecular theory, in all cases of chemical change the action is between molecules, such symbols as these ought always to be employed.
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.
He established the existence of molecules and atoms as we have defined above, and stated that the number of atoms in the molecule is generally 2, but may be 4, 8, &c. We cannot tell whether his choice of the powers of 2 is accident or design.
These atoms, which are the seeds of all things, are, however, not eternal but created by God.
The molecule of every compound must obviously contain at least two atoms, and generally the molecules of the elements are also polyatomic, the elements with monatomic molecules (at moderate temperatures) being mercury and the gases of the argon group. The laws of chemical combination are as follows: I.
The Daltonian would say that each of these weights represents a certain group of atoms, and that these groups can replace, or combine with, each other, to form new molecules.
It is evident that this is practicable if the number and kind of atoms contained in the molecule of a compound can be determined.
The assumption was arbitrary, based on no valid evidence.
It is now agreed that the molecule of water contains two atoms of hydrogen and one of oxygen, so that the atomic weight of oxygen becomes 16, and similarly that the molecule of ammonia contains three atoms of hydrogen and one of nitrogen, and that consequently the atomic weight of nitrogen is 14.
The symbols of compounds become very concise, as the number of atoms of one kind in a molecule can be expressed by a sub-index.
PYRIMIDINES, METADIAZINES or Miazines, in organic chemistry, a series of heterocyclic compounds containing a ring complex, composed of four carbon atoms and two nitrogen atoms, the nitrogen atoms being in the meta-position.
There is no such thing really as a vacuum, any more than there are atoms or ultimate indivisible particles.
In both these doctrines of a priori science Descartes has not been subverted, but, if anything, corroborated by the results of experimental physics; for the so-called atoms of chemical theory already presuppose, from the Cartesian point of view, certain aggregations of the primitive particles of matter.
It should be added that the modern theory of vortex-atoms (Lord Kelvin's) to explain the constitution of matter has but slight analogy with Cartesian doctrine, and finds a parellel, if anywhere, in a modification of that doctrine by Malebranche.
345), that only compounds containing two carbon atoms yielded fulminates, points to (Hcno) 2; on the other hand, Wohler (loc. cit.
The force which brings the atoms together in the forms of objects is inherent in the elements, and all their motions are necessary.
The real world thus arising consists only of diverse combinations of atoms, having the properties of magnitude, figure, weight and hardness, all other qualities being relative only to the sentient organism.
Their fundamental conception is that of Democritus; they seek to account for the formation of the cosmos, with its order and regularity, by setting out with the idea of an original (vertical) motion of the atoms, which somehow or other results in movements towards and from one another.
The world consists of a finite number of atoms, which have in their own nature a self-moving force or principle.
" The subsidiary rays of medals and inscriptions, of geography and chronology, were thrown on their proper objects; and I applied the collections of Tillemont, whose inimitable accuracy almost assumes the character of genius, to fix and arrange within my reach the loose and scattered atoms of historical information."
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.
The relative weights of atoms. He took hydrogen, the lightest substance known, to be the standard.
He denied that gaseous atoms could have parts, although compound gases could.
Hence the gaseous atoms of hydrogen and oxygen could not have parts.
His terminology was vague and provoked caustic criticism from Berzelius; he assumed that all molecules contained two atoms, and consequently the atomic weights deduced from vapour density determinations of sulphur, mercury, arsenic, and phosphorus were quite different from those established by gravimetric and other methods.
The gradual accumulation of data referring to organic compounds brought in its train a revival of the discussion of atoms and molecules.
Laurent generally agreed, except when the theory compelled the adoption of formulae containing fractions of atoms; in such cases he regarded the molecular weight as the weight occupying a volume equal to four unit weights of hydrogen.
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.
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.
He defined structure " as the manner of the mutual linking of the atoms in the molecule," but denied that any such structure could give information as to the orientation of the atoms in space.
He regarded the chemical properties of a substance as due to (1) the chemical atoms composing it, and (2) the structure, and he asserted that while different compounds might have the same components (isomerism), yet only one compound could have a particular structure.
An acid is said to be monobasic, dibasic, tribasic, &c., according to the number of replaceable hydrogen atoms; thus HNO 3 is monobasic, sulphuric acid H 2 SO 4 dibasic, phosphoric acid H 3 PO 4 tribasic.
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.
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.
If two compounds combined, the + signs of the free compounds were discarded, and the number of atoms denoted by an Arabic index placed after the elements, and from these modified symbols the symbol of the new compound was derived in the same manner as simple compounds were built up from their elements.
At a later date Berzelius denoted an oxide by dots, equal in number to the number of oxygen atoms present, placed over the element; this notation survived longest in mineralogy.
Berzelius objected to the hypothesis that if two elements form only one compound, then the atoms combine one and one; and although he agreed theory.
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.
Lucretius regards the primitive atoms (first beginnings or first bodies) as seeds out of which individual things are developed.
Atoms swerved as they fell endlessly downwards, and thus introduced an indeterminate or irrational element into the processes of the world.
Theism can take but little interest in this peculiar type of free will doctrine, or again in Epicurus's professed admission of the existence of gods - made of atoms: inhabiting the spaces between the worlds; Stoicism.
ACID-AMIDES, chemical compounds which may be considered as derived from ammonia by replacement of its hydrogen with acidyl residues, the substances produced being known as, primary, secondary or tertiary amides, according to the number of hydrogen atoms replaced.