﻿Distribution of Electrons in Na and CI Atoms. 449 



valency electron is transferred from the outer region of one 

 atom to that of the other, it will still be in the region between 

 the two atoms for the greater part of the time, since each 

 atom touches six neighbours, and the difference in the 

 diffraction effects will be exceedingly small. It is for this 

 reason that we think Debye and Scnerrer's results for LiF, 

 which were not absolute measurements such as the above, 

 were not adequate to decide whether the transference of a 

 valency electron has taken place. 



We have assumed that the atoms are ionized in calculating 

 our distribution curves. If, on the other hand, we had 

 assigned 11 electrons to sodium and 17 to chlorine, we 

 should have obtained curves of much the same shape but, 

 with an additional electron in the outermost shells of sodium 

 and one less in those of chlorine. 



9. Summary. — We have attempted to analyse the distri- 

 bution of electrons in the atoms of sodium and chlorine by 

 means of our experiments on the diffraction of X-rays by 

 these atoms. The results of the analysis are shown in 

 figs. 3 and 4. 



The principal source of er.ror in our conclusions appears to 

 be our ignorance as to the part played by "extinction" in 

 affecting the intensity of X-ray spectra. The distributions 

 of the electrons are deduced from the F curves (fig. 1). 

 The most important parts of these curves are the initial 

 regions at small angles, for errors made in absolute values 

 in this region alter very considerably the deductions as to 

 electron distribution. The exact form of the curve at large 

 angles is of much less interest. Now, it is in this initial 

 region, corresponding to strong reflexions such as (100) r 

 (110), (222), that extinction is so uncertain a factor. Until 

 the question of extinction is satisfactorily dealt with, the 

 results cannot be regarded as soundly established. 



If our results are even approximately correct, they prove 

 an important point. There cannot be, either in sodium or 

 chlorine, an outer " shell " containing a group of eight 

 electrons, or eight electrons describing orbits lying on an 

 outer sphere. Such an arrangement would give a diffraction 

 curve which could not be reconciled with the experimental 

 results. Eight electrons revolving in circular orbits of the 

 same radius would give the same diffraction curve as eight 

 electrons on a spherical shell, and are equally inadmissible. 

 On the other hand, it does seem possible that a combination 

 of circular and elliptical orbits will give F curves agreeing 

 with the observations. 



Phil Mag. S. 6. Vol. 44. No. 261. Sept. 1922. 2 G 



