On Nuclear Electrons. 



455. 



While this paper was in the press, I learned from 

 Dr. Niels Bohr, during conversation, that he has referred to. 

 the discrepancy between the two expressions in a footnote 

 on page 54 of his ; Dissertation ' (which is printed in Danish), 

 and has remarked that it is due to the erroneous method by 

 which Drude calculated the mean velocity communicated to 

 the electrons by the field. In spite of these facts, the parts- 

 of the present paper dealing with this matter will I think be 

 found of interest in indicating more precisely the exact 

 point, or rather points (for there are two) which are involved 

 in the rather subtle explanation of the discrepancy. 



XLIX. On Nuclear Electrons. By A. VAN DEN Broek * m 



THAT the intra-atomic charge is equal not to half the- 

 atomic weight, but to the number M each element 

 occupies in MendelejefFs series arranged in order of in- 

 creasing atomic weight, follows from the ratio of the scatter- 

 ing of ^-particles per atom divided by the square of that 

 number being a real constant (18*7 + 0*3 for Ou, Ag, Sn r 

 Pt, An), as according to Rutherford must be the case for 

 that ratio divided by the square of the charge, while if the 

 square of half the atomic weight is taken, these numbers 

 show systematic diminution from, if as mean value 18*7 too is 

 taken, 20*6 for Gu to 17*5 for Au f . 



Table I. 





Cu. 



Ag. 



Sn. 



Pt. 



Au. 



Mean. 



Scatterings--^— ... 



M 



Scattering -^M 2 



20-6 



29 



18-5 



189 



47 

 18-4 



181 



50 



190 



17-8 



82 



18-6 



17-5 



83 

 18-4 



18-6 



! 

 | 



186 ! 



I 



As these nuclear charges for U and Pb, as for Th and B^,. 

 give other differences than the number of positive charges- 

 lost by expulsion of the a-particles (the nuclear charge 

 difference being 10 for U and Pb, and 7 for Th and Bi > 



* Communicated bv the Author. 



t Geiger & Marsdeii, Phil. Mag. xxv. p. 604 (1913). 



