the 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES.] 



MA Y 1914. 



LXXXVIII. The Forces between Atoms cin$ Chemical 

 By Sir J. J. Thomson, O.M., 



IF the atom is a mixture of negatively electrihecrctrrprrscies 

 and positive electricity, it will produce in its neigh- 

 bourhood a field of electric force. For even when the atom 

 contains equal amounts of positive and negative electricity, 

 the effects of the opposite charges will not wholly counter- 

 balance each other since these charges are in different parts 

 of the atom : there will still be a field of force though the 

 forces will diminish more rapidly than the inverse square 

 of the distance and will also not be uniformly distributed 

 round the atom. These forces will be exerted by the atom 

 not merely on the atoms which are associated with it in the 

 molecule of a chemical compound, but also on the atoms in 

 other molecules, giving rise to forces between the molecules 

 and producing thereby the intrinsic pressure and surface 

 tension of liquids, latent heat of evaporation, cohesion of 

 solids and liquids, the rigidity of solids, and so on. These 

 physical phenomena are the effects of forces between different 

 molecules, whereas chemical affinity and chemical pheno- 

 mena in general are the effects of forces having the same 

 origin but acting between the atoms in the same molecule. 



The consideration of the mutual action between atoms is 

 perhaps the most important part of any atomic theory, for 

 on it depends the explanation of the majority of chemical 

 as well as of physical phenomena. 



* Communicated by the Author. 

 Phil. Map. S. 6. Vol. 27. No. 161. May 1911. 3 E 



