SectiOxX III, 1922 [49] Trans. R.S.C. 



On an Application of the Theory of Magnetism to the Calculation oj 



Atomic Diameters 



By J. F. T. Young, M.A. 



Communicated by Professor J. C. McLennan, F. R.S.C. 



(Read May Meeting, 1922) 



I. Introduction 



During the course of some advanced work on the theories of 

 magnetism the attention of the writer was directed to the possibiHty 

 that the modern conceptions of the structure of the atoms, as pro- 

 posed by Bohr or by Lewis and Langmuir, might be utiHzed in con- 

 junction with the theory of magnetism, developed on the basis of the 

 electron theory by Langevin and extended by Weiss, Kunz, Honda 

 and others, to deduce an estimate of the atomic diameters of the 

 elements. At the same time some rather striking relations of the 

 magnetic properties of the families of the elements as arranged in the 

 periodic system came to light and have been briefly summarized in 

 the first part of the paper, without attempting in too great detail to 

 correlate them to the structure of the atoms concerned. Indeed, 

 until the probable arrangements and motions of the electrons of the 

 atomic systems have been more thoroughly tested both by a theoretical 

 survey of the conditions of stability of the atomic structures proposed 

 and, on the experimental side, by investigations of the conditions 

 necessary for the production of the different types of spectra of the 

 elements and the correlation of these to definite processes in the 

 atomic system, the magnetic properties of the elements, like the 

 chemical properties, can serve only in a qualitative way to direct the 

 efforts towards solving the problem of atomic structure. 



In the second part of the paper there has been given the mathe- 

 matical development of the relation between the atomic radius and 

 the magnetic permeability of the elements. The final form of the 

 result shows that the area of the electronic orbits in the atom has a 

 very simple connection with the permeability of the element con- 

 cerned and the mass and charge of an electron. The limitations of 

 the theories of magnetism are such that the result applies only for 

 the diamagnetic elements. 

 4— c 



