322 Prof. W. D. Harkins on the 



The above facts lead to the hypothesis that relative 

 instability is the result of the presence of an odd number of 

 negative nuclear electrons, either an instability of the 

 nucleus, or an instability of the group containing the odd 

 electron, this group being essential for the formation of the 

 nucleus. In order to test this hypothesis we may turn to 

 the radioactive atomic species (Table VI.), where the 

 stability of the nuclei is known in terms of their average 

 periods of disintegration. It should be remarked that in 

 considering nuclear instability mention should be made of 

 the type of instability, which in the radioactive series would 

 be instability with reference to beta particle emission. 



Table VI. 



Effect of an Odd Number of Negative Nuclear Electrons in 

 Producing Nuclear Instabilitf. 



Atomic 



Species. 



N 

 ( = eveu). 



N=even 



Average 



Life. 



N = odd 



Average 

 Life. 



N 

 ( = odd). 



Atomic 



Species. 



TJX, 



144 



35'5 days 



1'85 min. 



143 



UX 2 



Me Th x 



140 



9*6 years 



8*9 hours 



139 



MsTh a 



RaD .... 



128 



24 years 



7*2 days 



127 



EaE 



The above comparison indicates an extremely striking- 

 difference in each case between the periods, and shows that 

 in each case the disintegration is much more rapid when the 

 nucleus contains an odd number of electrons, about 50,000 

 times more rapid in the first case, 18,000 in the second, 

 and 2,200 in the third. The effect is not so striking in cases 

 where there is a splitting of the series, but is in all cases in 

 the proper order in the thorium and uranium series. It 

 seems likely that in such a complex structure as the nucleus 

 of a heavy atom there may be some exceptions to this general 

 relationship, but none have been found thus far. Unfortu- 

 nately, the atomic weight of none of the members of the 

 actinium series is known, so the relations in that series 

 cannot be listed. It is evident that they are not quite so 

 simple as in the other two series. 



When the above facts are taken into consideration, and 

 especially since there seem to be two negative electrons in 

 the alpha particle, — the most important group in nuclear 

 building, — it seems that the following statement is justified : 

 The negative electrons in atom nuclei seem to be 



