574 W^CKOFF: FORCES BETWEEN ATOMS IN SOLIDS 



lets will exist within an atom possessing electrons and a pos- 

 itively charged nucleus.^' The formation of the clusters of eight 

 electrons so condenses together the lines of force about the atom 

 that their moments with respect to other atoms are nearly negligible. 

 Where the outside loosely bound electrons are concerned, the 

 fields about the doublets become of the utmost importance in 

 determining the chemical and physical properties of bodies. 



Magnetic fields of the atom. — This discussion has taken no 

 account of the magnetic fields about the atom. That atoms 

 are possessed of fields of their own is shown by the effect of large 

 outside fields upon the spectrum lines, — the Zeeman effect — 

 and by various other lines of evidence. ^"^ It is probable that a 

 detailed discussion of these magnetic effects would remove many 

 of the difficulties arising from the application of such a theory 

 as the present one. Certainly such a discussion must accom- 

 pany any entirely general or quantitative theory. The "mag- 

 neton" theory of A. L. Parson^ is an attempt in this direction. 

 Contradictions to some of the most commonly accepted ideas 

 (such as the point-electron and the Rutherford type of atom) 

 which Parson's theory presents make it simpler to neglect, at 

 present, consideration of magnetic phenomena. It is probable 

 that the magnetic forces influence in a marked degree the in- 

 tensity of bonding between atoms but that their consideration 

 will not introduce any new kinds of linkage. 



Forces between atoms. — Conditions of equilibrium require the 

 action of forces of attraction and repulsion. Uncertainties con- 

 cerning the size of the atom make themselves felt in a considera- 

 tion of the forces of repulsion . We find that the distance be- 

 tween the atoms in a solid ^^ is of the order io~^cm. The actual 



most part concentrated in the small space between the charges, so that the in- 

 tensity of the field at any point (m) at a distance from both charges is slight. In 

 other words, the moment of the doublet with respect to the point is small. If 

 the separation of the charges is greater, the field will be more spread out, more 

 lines of force will pass through m, and the moment of this new doublet with respect 

 to m is much greater. 



2* J. J. Thomson, op. cit. 



2« See W. J. Humphreys. Science, N. S. 46: 273-279. 1917. 



2" W. H. Bragg and W. L. Bragg. X-rays and crystal structure, Chap. VII. 



