*(•' . / • -A’ & J 
f)Sk 
iu 
HBtadjj: 
'.andto; 
■6foro; % 
todealiith 
“st3 tint ieb 
a snggalst 
s may, in ¡e? 
Bek BBgKi 
both for oj£ 
] dealt lij 
probafciv ¡G: 
etonäis 
out ki 
lead to me 
; t appears E 
also louse 
a oagnetici 
ins. Souk 
solved, tliefe 
>en made k - 
¡n and Cek 
■agnetic salts; 
solid state, 2 
oe, are ante 
rdancewt! 
V.Pt 
111 1 ! 
ether ii 02 
, voL 3 2 ’ 
VII. 4] 
MAGNETISM 
99 
has been developed by Sommerfeld.* The classical formula 
for the relation between the magnetic moment M and the impulse 
moment J is 
M 
2 m 
7 ■ i3 
It is proposed to modify this by the introduction of a “ splitting 
factor ” g so that 
2 m 
7:14 
The theory of Pauli and Sommerfeld gives a good general 
account of the magnetic properties of the elements of the fourth 
period. 
Sommerfeld considered the s-state of the atom for which 
k = 1. However, the normal state of many atoms and ions 
corresponds to a higher value of the quantum number k, which 
implies an increase in the allowable magneton numbers. 
4. Magnetism and the Structure of the Atom 
The work of Moseley, who systematically investigated the 
X-ray spectra of numerous elements, proved that all elements 
have, on the whole, the same X-ray spectrum, the lines shifting 
with increasing atomic number towards increasing frequency of 
vibration. The close similarity between X-ray spectra shows 
that all atoms have the same internal structure, while the chemical 
and optical properties are controlled by the outer structure. 
These results led to the view that the electrons are arranged 
in a series of shells round the nucleus, a view that was developed 
by Lewis, Langmuir, Kossel and others, and was found capable 
of supplying a qualitative explanation of a wide range of observed 
phenomena. According to the later development of Bohr’s 
theory of the structure of the atom, a shell should be regarded 
not as a separate region of space but as a closely bound group 
of electrons, characterized by certain particular quantum 
numbers. An individual electron in a group may sometimes 
approach the nucleus, sometimes recede from it to a considerable 
distance. An atom is supposed to be formed by the successive 
capture and binding of the electrons one by one in the field of 
force surrounding the nucleus. Bohr’s views as to the magnetic 
properties of the elements are summarized in the following 
quotation from an address delivered in 1921.! 
* See Phys. Zeits., vol. 24, p. 360, 1923 ; Zeits. f. Physik, vol. 19, 
p. 221, 1923 ; Ann. d. Physik, vol. 73, p. 209, 1924. 
t The Theory of Spectra and Atomic Constitution, p. 106 (Cambridge, 
1922). 
8