A system of physical chemistry - Index of

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A system of physical chemistry - Index of

122 A SYSTEM OF PHYSICAL CHEMISTRY

relation, already discussed, between the frequency of emitted radiation

and electronic charge involves the square of the latter. In other words,

the square root of the frequency emitted is proportional to e itself.

Bohr's relation, in fact, is capable of predicting the characteristic X-ray

radiation from an element of high atomic weight with considerable

exactness. In this connection it may be pointed out {cf. Millikan

Physical Review, Aug., 191 7) that the orbit of the innermost electron

is inversely proportional to the atomic number or nuclear charge, i.e.

the greater the charge on the nucleus the smaller the radius of circular

path followed by the innermost electron.

Characteristic Infra-red Frequency and Atomic Number.

An interesting relationship has been pointed out by Allen {Proc.

Roy. Soc, A, 94, 100 (1917)) between the atomic number and the infrared

frequency which accounts approximately for the atomic heat of the

element. Writing N for the atomic number and v for the frequency of

a giyen element, Allen's relationship is—

where n is an integer called the frequency number, and v^ is a fundamental

constant the same for all elements. The mean value for i/^ is

2 1

-3 X io^^\ The following table illustrates the above relation. The

experimental values of r for the various elements (obtained from atomic

heat measurements of Nernst, Grififiths, and Keesom-Onnes) have

been multiplied by the atomic number N.

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