﻿Disintegration of Elements by a Particles. 

 Table T. 



429 



Element. £ t01 » ic 

 a amber. 



h r~ 



He 2 



Li 3 



Be 4 



B 5 



c" 6 



N 7 



O 8 



Fl 9 



Ne 10 



Atomic 

 Masses. 



1-008 



400 



6,7 



9 

 10,11 

 12 

 14 

 16 

 19 

 20,22 



Element. ,£ toD ? io 

 .Number. 



2ii IT - 



Mg 12 



Al 13 



Si 14 



P 15 



S 16 



CI 17 



A 18 



K 19 



Atomic 

 Masses. 



23 



24, 25. 26 



27 

 28.29 



31 



32 

 35,37 

 36,40 

 39,41 



An examination of the table shows that the active elements 

 may be classified in different ways : — 



(1) Active elements are odd-numbered elements in a 



regular sequence of numbers, viz., 5, 7, 9, 11, 13, 15. 



(2) The atomic masses of the active elements are given by 



472 + a where n is a whole number ; a = 3 for all the 

 elements except nitrogen, for which it is 2. 



(3) With the exception of boron, which has two isotopes 



(10, 11), the active elements are all pure elements. 



We have seen that no evidence has been obtained that the 

 preceding element lithium (3), and the succeeding elements, 

 chlorine (17) and potassium (19), show any trace of activity 

 under a-ray bombardment, although they are odd-numbered 

 elements and the masses of their isotopes are given by 4n-f- a. 

 Magnesium and silicon, which are even-numbered, but which 

 contain isotopes of mass 4?i -t- 1 or 4n + 2, show no sign of 

 activity. 



There thus appears to be no obvious general relation which 

 differentiates active from inactive elements. The activity 

 starts sharply with boron and ends abruptly with phosphorus. 

 It is a very unexpected observation that neither lithium nor 

 chlorine shows any certain evidence of activity in the emission 

 of either long-range or short-range particles. It is of 

 interest to consider whether any deduction can be made as to 

 the structure of these nuclei in the light of these experimental 

 facts. 



In our previous paper it was pointed out that the H nuclei 



