NO. II 



STRUCTURE OF THE ATOM PARSON 



51 



would expect from what is known of the cohesion of these two sub- 

 stances, especially in view of the fact that the Iron atom has eight 

 valence magnetons and the Argon atom none. The assumption that 

 the envelope of the Iron atom is already compressed to a very small 

 volume (as shown in the figure) is justified by the exceedingly low 

 compressibility of this element — as found by T. W. Richards. 



The curve of atomic volumes. — Owing to the complexity of the 

 factors involved, it is useless to try to make up an expression that 

 would yield a complete atomic volumes curve ; but it is nevertheless 

 possible to predict a number of the features of such a curve. 



Qji& cnn (ii£[^ Jd). 



j^u m (&°& A\ 



( GUcwu^ UD-Cu/mtA 5.?* 



In the first place, the force that compresses the atoms is likely to 

 come chiefly from the valence magnetons, and to a less extent from 

 the groups of eight in the atom. Now the slight cohesion of the 

 inert elements shows that the latter factor is small enough to be 

 neglected when there are valence magnetons present — in the present 

 rough treatment at any rate. It is important, however, to find out 

 the effective numbers of the valence magnetons in the various atoms. 

 That these are not necessarily the same as the actual numbers may 

 readily be seen by comparing the probable behavior of CI (2y + 7) 

 with that of Mn (3y + 7). The former has a strong tendency to 

 form the group of eight, and so in its cohesive action it will 

 behave as if it contained fewer than seven magnetons. This argu- 

 ment applies to all the halogens, and to a less extent to the nega- 



