the Ahsorpticn of X-Ra.ys, 191 



exhibited in the figure fall a little above the straight line that 

 represents the group. In the group Cr — Ni the number of 

 outer electrons is 6-10 respectively ; but presumably there 

 are in these elements two or more electrons more closely 

 attached to the nucleus, as we found it likely to be the case 

 for C and Si. 



At Cu the outer electrons would be 5, which will then 

 successively be augmented by one electron at each element 

 of the following group. Now it does not seem very likely 

 that in so great a number of outer electrons as would be 

 present in the outer region for the latter elements in this 

 group all the electrons would occupy an equivalent position. 

 Possibly here, too, some kind of ring formation may take 

 place by means of w T hich certain among the outer electrons 

 may concentrate towards the inner region and so more closely 

 adhere to the nucleus. Thus the circumstance pointed out, 

 that fc a /Q u in the latter elements of this group is somewhat 

 greater than what ought to have been the case if the 

 formula (7) were quite correct, might be explained. 



We may well anticipate that the just mentioned re- 

 arrangements may be perceivable in the X-ray spectra of the 

 elements. As Sommerfeld * has made probable, the N-ring 

 ought to commence by Mg and the M-ring by Ca. This is 

 in good agreement with my results. That there are no new 

 lines in the spectra of S and Cr — as up to the present had 

 been detected — may be explained easily, if we assume that 

 by rearrangements of the electrons no new ring has been 

 formed, but only the number of electrons in the already 

 existing inner rings has been increased. The sudden increase 

 in absorption by Z = 29 (or perhaps Z = 30) seems to stand 

 in some relation to the at-this-point-beginning L-series, 

 which, after our present knowledge, just begins at Z = 30. 

 This question is, however, not so simple, as it is not 

 evidently proved that elements with lower atomic number 

 than 30 do not show L-lines. Perhaps these lines have escaped 

 detection owing to their considerably great wave-length. 



In Table IX. there is an arrangement indicating, in 

 accordance with what is said above, the most probable 

 distribution of electrons betw r een the inner and outer region 

 in the first 23 elements. The first figure given for the 

 respective elements indicates the number of electrons in 

 the inner region and the second figure gives the number of 

 electrons in the outer region. The elements are arranged in 

 accordance with the periodic system. 



* Sommerfeld, Phys. Z. xix. p. 298 (1918). 



