336 Prof. W. D. Harkins on the 



last is constituted o£ one alpha particle plus two negative 

 cementing elections. The two electrons in the alpha particle 

 (/> 4 <? 2 ) are more tightly bound and may be designated as 

 binding electrons. 



The Structure of Atom Nuclet. 



The structure assumed for a complex nucleus should be 

 such as to account for the relations discussed in the preceding 

 sections. 



1. The considerable magnitude of the loss of mass (0*76 

 per cent.) in the formation of complex atoms indicates 

 that the protons, which have practically all of the mass, 

 should (a) lie far apart from each other in comparison 

 with their own radii ; (/>) lie relatively close to the 

 negative electrons. These considerations are not based 

 on, but need not exclude, kinetic effects, since thev 

 refer merely to the mean positions of the particles. 



2. The fact that in the most abundant atomic species one 

 negative electron binds two protons Q^Xr 



A theory which naturally suggests itself, and which is in 

 accord with the deductions made with regard to the relative 

 sizes of the electrons and protons by means of the electro- 

 magnetic theory, is that both 1 and 2 are natural results of 

 the small size of the proton as compared with the electron. 

 The doubtful feature is that which relates to the changes in 

 the theory which may result from the introduction of the 

 newer generalized relativity. At any rate the two facts 

 listed above and the electromagnetic theory relations may be 

 harmonized. According to the latter the proton has been 

 assumed to have a radius of the order of 1/1835 that of the 

 electron. Calculations made for the writer by Prof. A. C. 

 Lunn showed that the observed packing effect could be 

 accounted for on the basis of the electromagnetic theory if 

 the distance between the centres of the proton and the 

 electron is 400 times the radius of the former, the supposedly 

 smaller particle. This would indicate that the protons may 

 be assumed to be very close with what may be termed the 

 outer part of the electron. Since the proton is small, 

 according to such a supposition,, two or three protons might 

 be held by one electron, as illustrated in fig. 8, which also 

 gives a possible model for the alpha particle. There may 

 be some other form for the latter which will meet the above 

 conditions and still suggest a possible method of disintegrating 



