728 Prof. Harkins and Mr. Wilson on Energy Relations 



the nebulae, other than the system le, can have simple, or 

 non-structural nuclei when they contain several charges of 

 the same sign. It is contrary to our experience to find 

 charges of the same sign packed close together unless there 

 is some " matter " to which they are attached. 



Moreover, in calculating the distances apart of the alpha 

 particles in the radioactive elements, Nicholson uses an atom 

 whose nucleus is made up of a simple positive charge of ne 

 plus another positive charge of 2e, also simple, and two 

 negative electrons. Around this rotate enough negative 

 electrons to make the atom neutral. In the first place, the 

 part of the nucleus represented by the term ne cannot be 

 simple. As Nicholson himself states, it is recognized that 

 there are negative electrons in the nuclei of the radioactive 

 elements, and while in this case he assumes that there are two 

 present, other considerations lead to the conclusion that these 

 are not enough. It must be kept in mind that the mass of 

 the elements has to be accounted for, and to do this it is 

 necessary that the number of positive units (if they are 

 hydrogen nuclei) in the nucleus must be approximately 

 equal to the atomic weight of the element. Then in order 

 that the resultant charge on the nucleus be equal to the 

 atomic number, as Moseley's work demands, a certain 

 number of negative electrons must be included, and this 

 number is not far from one-half the atomic weight. If the 

 elements are built up according to Nicholson's own system, 

 they would have to contain a much larger number of both 

 kinds of electrons. 



Also, the mass of the alpha particle, which is described as 

 consisting of a simple charge of 2e, is entirely unaccounted 

 for. If Nicholson is right, and the positive electron has a 

 mass of about 0*081, the mass of the alpha particle could 

 only be 0*324 at the most, using Nicholson's law that for 

 the simple elements the atomic weight is proportional to the 

 square of the atomic number. Even if the hydrogen nucleus 

 is considered to be the positive electron, a system consisting 

 of two such charges would not (unless by Nicholson's theory 

 for simple elements) account for an atomic weight of four. 

 It seems probable that the helium nucleus must be built up 

 of four hydrogen nuclei and two negative electrons ; so it is 

 difficult to see how any calculations of distances involved in 

 complex atoms based upon the assumption that the helium 

 nucleus is simple, can be correct. 



The consideration of the law of radioactive change which 

 was developed by Fajans, Soddy, and others, leads to a 

 regular and simple system for the structure of the atoms. 



