On the forces between atoms and ions

The ultimate knowledge which we can hope to derive from many of the physical properties of gases and crystals is that which concerns the nature of the forces between the constituent atoms and ions. In terms of these forces many diverse phenomena both of gases and solids should be explicable. In some recent researches the writer has sought to determine the repulsive part of the forces between certain atoms and ions in terms of inverse power laws. This representation is considered superior to the treatment of atoms and ions as rigid spheres with definite diameters, as is generally done, for it permits of the correlation of the physical properties of a gas with those of certain associated crystals. Thus the forces which explain the thermal conductivity of neon have been shown to explain as well the observed spacing constants of crystals like NaF and MgO. These researches had their starting point in an investigation of certain physical properties of the pure gases, and this formed a necessary preliminary step to the later work on crystals. The methods there developed were, however, applicable only to neon and argon, for only in those cases was the necessary experimental information available. Consequently the later extension to include the forces of ions applied only to ions of similar electronic structure to these gases.