Atoms and Molecules. 893 



the residual atom is, therefore, 12 — 7 = 5 units, and the total 

 mass is 12. 



In considering the breaking up of the oxygen ring it may 

 be supposed that it is cut in two along the line 00' indicated 

 in fig. 3. This will leave a portion which, however, will have 

 lost one electron from each doublet, and thus the number of 

 electrons left is 7 and the positive charge is 12 and mass 12, 

 namely, exactly the same combination as obtained from 

 nitrogen above. The geometrical form cannot remain as a 

 portion of a ring on account of the repulsion of the two ends, 

 and seems likely to adjust itself to exactly the same more 

 stable form of fig. 2. 



In going over the calculations of Rutherford* undertaken 

 for the purpose of finding the mass of the unknown atom 

 from his observations, it is found that he has begun with an 

 assumption not experimentally well substantiated, that the 

 unknown atom carried a charge of two units. If, for the 

 moment, it be granted that this charge might possibly have 

 been five units, then the ratio of the charge E' of the unknown 

 atom to the known charge E = 2 of the alpha particle, which 

 ratio now becomes 5/2 instead of unity, will have to be carried 

 all through the subsequent work. Doing this results in the 

 equation 



1-U MVE'= 1-25 muB, 



instead of his equation (1). Combining this with his 

 formula (2), which will remain unchanged, results in the 

 values for the unknown atom : 



m = 12-1, 

 u = 0-76 V, 

 and x = 9 cm. = the observed range. 



It does not seem a safe procedure to base deductions upon 

 the original energy of the alpha particle and assume that 

 this is the only energy available because, if the energy 

 is sufficient to break up the atom, there becomes available 

 another source of energy which must affect the velocities of 

 the parts of the atom, the residue, and this energy is now 

 unknown. Thus the unknown mass comes out 12 instead of 3 

 and is in agreement with the conception that this unknown 

 atom is the residue from both nitrogen and oxygen, having 

 a charge of 5 units. The percentage 121/120 is a little closer 

 agreement than that found by Rutherford as 31/30, though 

 this is of little moment. If the above turns out to be a 



* Bakerian Lecture, 1920, Prc-c. Roy. Soc. ser. A, vol. xcvii. No. a 686, 

 p. 390. 



