Constitution and Stability of Atom JSnclei. 331 



such a nucleus could be formed in one step by all of the 

 232 positive and 142 negative electrons coming together in 

 the proper space relations to give stability, so it might be 

 supposed that either of the electrons adds on one at a time, 

 beginning with the formation of a single neutron, and that 

 then positive and negative electrons attach themselves one 

 at a time, approximately two of the positive type attaching 

 themselves for each which is negative. However, the facts 

 concerning the atomic weights and the abundance relations 

 indicate that it is much more probable that there is first the 

 formation of electron-proton groups, mostly of masses of 4 r 

 3, 2, and possibly neutrons of mass 1, and that these unite 

 to form the more complex nuclei. While there may be 

 primary electron groups of higher mass, there is nothing in 

 the facts as now known which makes it necessary to make 

 such an assumption. 



The Alpha Particle as the Most Abundant 

 Electron Group*. 



In a series of papers, the first of which was published in 

 1915 under the title " The Hydrogen-Helium System/' the 

 writer endeavoured to show that the alpha particle of mass 4 

 and positive charge 2, is the most abundant o£ these electron 



Table VII. 



FoRMULiE EXPRESSING THE ATOMIC WEIGHT AND NUCLEAR POSITIVE 



Charge of the Light Atoms of Even Atomic Number f. 

 (Most abundant Isotope only.) 



Atomic 





Nuclear 



Atomic 





Nuclear 



Number. 



Element. 



formula. 



Number. 



Element. 



formula. 



6 



C 



«3 



18 



A 



«10«* 



8 







«4 



22 



Ti 



a l2 e 2 



10 



Ne 



Cl 5 



24 



Cr 



«13«2 



12 



Mg 



a G 



26 



Fe 



a xi e 2 



14 



Si 



a 7 









16 



S 



a s 









18 



(A) 



K) 









20 



Ca 



Ko) 









groups, and that those of masses 3 and 2 are considerably 

 less evident. This is most simply expressed as in Table V 1 1 .. 



* While the earlier formulae given for nuclei by the writer wove 

 expressed in Greek letters, the present nomenclature was adopted for 

 use in a paper in ' School Science and Mathematics,' May and June. L920, 

 except that p is here substituted for h. "While tins was done to indicate 

 "positive," it happens to be the initial letter of the word proton, recently 

 suggested by Sir Ernest Rutherford as a distinctive word to designate 

 the hydrogen nucleus. 



t In this Table a represents an alpha particle, presumably ;y' : . 



