﻿THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



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.•■to \& L 



[SIXTH SERIES.] r\£"\ I- 



OCTOBER 1922. 



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5, P- 



LVI1I. Further Studies on the Electron r Theory of Solids. 

 The Compressibilities of a Divalent Metal and of the 

 Diamond. Electric and Thermal Conductivities of Metals. 

 By Sir J. J. Thomson, O.M., F.R.S.* 



IN a paper published in the Philosophical Magazine,, April 

 1922, I calculated on the Electron Theory of Solids 

 the compressibility of monovalent and trivalent elements 

 crystallizing in the regular system. In this paper I propose 

 to do the same for a divalent element. The simplest case 

 is that of calcium, for Hull has shown that it crystallizes 

 in the regular system and that the atoms are arranged in 

 face-centred cubes. Thus, as far as the atoms are concerned, 

 the metal may be supposed to be built up of cubical units, 

 each unit having | of an atom at each corner and ^ of an 

 atom at the centre of each of its six faces. Thus each unit 

 contains four atoms ; and as calcium is a divalent element, 

 there must be twice as many disposable electrons in the 

 unit as there are atoms, so that each unit must contain 

 8 electrons. 



A symmetrical way of arranging these 8 electrons is to 

 put \ of an electron at the middle point of each side of the 

 unit cube, one electron at the centre of this cube, and one 

 electron at the centres of 4 out of the 8 small cubes into 

 which the unit cube is divided by planes bisecting its sides 

 at right angles, These 4 cubes are chosen so that if we 



* Communicated by the Author. 

 Phil. Mag. S. 6. Vol. 44. No. 262. Oct. 1922. 2 U 



