788 Forces between Atoms and Chemical Affinity. 



electropositive elements the number o£ tubes of force will 

 be halved. We can easily see this, because when the cor- 

 puscles leave the atoms they carry with them ail the tubes 

 o£ force which left the atom ; thus, while before the trans- 

 ference of the corpuscles took place there were as many 

 tubes entering each atom as leaving it, after the transference 

 no tubes will leave the electropositive atom and none enter 

 the electronegative ones. The number of tubes will thus be 

 halved. And in this case we can easily see that they are 

 represented by the symbols representing the bonds on the 

 usual valency theory. Thus, when there is intra- molecular 

 ionization, we see that our theory leads to the same condition 

 for saturation as the usual one. We have seen, however, 

 that when there is no transference of corpuscles there is a 

 difference between the theories, and many compounds are 

 valency ones on the new theory, though they are not so on 

 the old. 



From this point of view compounds are to be divided into 

 two types according as their molecules do or do not contain 

 charged atoms. The valency considerations for compounds of 

 the second type are more elastic than for those of the first, 

 inasmuch as an atom when it occurs in a compound of the 

 second type may be regarded as having twice as many bonds 

 as when it occurs in a compound of the first type, the number 

 of bonds in this type of compound being the same as that on 

 the usual theoiy of valency. 



The compounds which are compatible with this theory of 

 valency, but incompatible with the old, will be mainly ring 

 or long chain compounds, and so are unlikely, unless they 

 contain carbon atoms, to have any great stability. It must 

 be remembered that fulfilment of valency conditions does 

 not ensure stability or the possibility of existence under 

 ordinary circumstances ; other conditions have to be satisfied 

 for this to be possible. 



The view we have taken or saturation is that when each 

 of the mobile compounds in an atom is anchored by a tube 

 of force passing to a neighbouring atom, the average attrac- 

 tion of the atom on other atoms is reduced to a minimum. 

 It must, however, be remembered that in consequence of the 

 dissociating effects due to heat, molecules can exist in a free 

 state at a temperature 6 when the work required to separate 

 an atom from the molecule is not considerable in comparison 

 with the average kinetic energy of the molecule at the tem- 

 perature 6. The existence of unsaturated compounds is thus 

 what we should expect from thermodynamical considerations. 



