A system of physical chemistry - Index of

booksnow2.scholarsportal.info

A system of physical chemistry - Index of

RUTHERFORD-BOHR ATOM-MODEL 113

the arrangement of the inner electrons. The fact that the period in the

chemical properties of the elements after the iron group is no longer

eight but eighteen suggests that elements of higher atomic weight contain

a recurrent configuration of eighteen electrons in the innermost

rings. The deviation from 2, 4, 8, 16 may be due to a gradual interchange

of electrons between the rings as already indicated when speaking

of the confluence of rings. Since a single ring of eighteen electrons

will not be stable, the electrons may be arranged in two parallel rings.

Such a configuration of the inner electrons will act upon the outer

electrons in very nearly the same way as a nucleus of (N

-

18)

x e.

It is conceivable that with increase in N another configuration of the

same type will be found outside the first, such as is suggested by the

presence of a second period of eighteen elements.

Systems Containing

Several Nuclei. Molecules.

According to Bohr a simple molecule such as the molecule of hydrogen

consists of two positively charged nuclei, each carrying unit charge

with a ring of two electrons rotating between them, the rotation being

round the line joining the two nuclei. If the two nuclei are similar in

all respects the electron ring rotates at a position midway between the

nuclei, the plane of the ring being perpendicular to the line joining the

nuclei. If the nuclei be dissimilar the ring will rotate at some position

lying nearer the heavier and more complex nucleus.

The equilibrium of such a system is conditioned as before by the

constancy of the angular momentum of each electron, along with the

further condition that W—the energy emitted in binding an electron to

the — system is a maximum.

Consider a system consisting of two positive nuclei of equal charges,

and a ring of electrons rotating round the line joining the nuclei. Let

the number of electrons be n, the charge on each be e, and the charge

on each nucleus be N^. It can be shown that the system will be in;

equilibrium if (i) the nuclei are equidistant from the ring and if

(2) the

ratio between the diameter of the ring, 2a, and the distance apart of the

nuclei, 2b, be given by—

.=

More magazines by this user
Similar magazines