A system of physical chemistry - Index of

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A system of physical chemistry - Index of

112 A SYSTEM OF PHYSICAL CHEMISTRY

ring will always be odd or even according as the total number df

electrons in the atom is odd or even. This suggests a relation with the

fact that the valency of an element of low atomic weight is always odd

or even according as the number of the element in the periodic series

is odd or even.

The fact that several considerations have been introduced into the

problem shows that the criterion of stability—

constancy of angular

momentum and a maximum value for W— is not sufficient to determine

completely the constitution of an atomic system. In very simple cases

the constitution of the atom is in relatively little doubt. It is possible,

however, by making use of all the foregoing considerations to arrive at

a moderately satisfactory statement of the constitution of atoms which

contain up to twenty-four electrons, that is, up to an atomic weight

of forty-eight approximately. Bohr gives the following table for these

atomic systems. The large numeral indicates the value of N, the total

number of electrons in the neutral atom, whilst the smaller figures in

brackets give the composition of the rings starting from the innermost.

Thus the symbol 9 (4, 4i i) denotes a neutral atom which contains in

all nine electrons, arranged in three concentric rings, the innermost ring

containing four electrons, the second likewise four, and the outermost one

electron, thereby indicating that the normal valency of this atom is one.

The atomic weight of the element in is question approximately 2x9

= 18, i.e. fluorine. It will be observed that Bohr places hydrogen

along with the halogens, and not with the alkali metals. Bohr does not

give the name of the corresponding element to these configurations but

the attempt is here made to do so.

Probable

Table Showing Structure of Atoms.

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