﻿564 



Mr. D. Coster on the Spectra of X- 



data about the binding o£ the 3 3 electrons in this region can 

 only be obtained for Cu and Zn, for which elements the 

 M-shell even has been completed. For this purpose we may 

 compare the frequency of the line K/3 2 with the sum of the 

 frequencies of Ka x and La lt They are given in Table XXVI. 



Table XXVI. 

 Frequencies. 





K/3 a . 



Xa 1 -l-L« 1 . 



Cu 



Zn 



661-30 



709-87 



661-24 



710-89 



The values for the K-lines have been taken from the new 

 measurements of Siegbahn and Dolejsek *, the La x line has 

 been determined by Hjalmar. This table shows that the 

 binding energy of the 3 3 electron for these elements is not 

 much different from that of tlfe electrons which are present 

 in the N-shell. 



For Ag the N-shell has been completed for the first time 

 into a shell of three subgroups of 6 electrons each and 

 respectively with the quantum symbols 4j, 4 2 , and 4 3 . From 

 a comparison of the Lj-absorption edge and the line L/3 2 it 

 appears that for this element the binding energy of the 

 4 3 -electron is. not more than 10 volts, thus being of about 

 the same magnitude as the energy of the 5-electron which is 

 already present. For the elements with higher atomic 

 number, however, the binding energy of the 4 3 -electron 

 increases more rapidly than that of the 5 1 -electron. 



In the same way it appears from a comparison of the 

 frequencies of: the line L/3 5 and the absorption edge Lj for 

 Au, where according to Bohr the O-shell even has been 

 completed into a shell containing six 5 l5 six 5 2 , and six 

 5 3 -electrons, that for this element the 5 3 -electrons are bound 

 with nearly the same energy as the 6 r electron. 



In this connexion it may be pointed out that the rare- 

 earth metals form a particular group of elements which in 

 certain respects has no analogy in the periodic system. In 

 fact, as the N-shell develops from a shell of three sub- 

 groups, each of six electrons, with the quantum symbols 4 l5 

 4 2 , and 4 3 into a shell of four subgroups, each of eight 

 electrons, with the quantum symbols 4 l5 4 2 , 4 3 , and 4 4 , the 

 O-shell has already a certain completion, which was first 



* Siegbalm and Dolejsek, Zeitschrift fur Physik, x. p. 159 (1922). 



