CHEMISTRY OF THE EARTH 101 



molecule of an aggregate of molecules, is 

 completely saturated, and there is no atomic 

 affinity between the molecules. This is entirely 

 different from the point being described here 

 of the building up of a giant single molecule 

 by the aid of the carbon atom. For this 

 latter purpose, the central or building atom 

 must have a high valency, and yet the valency 

 must not exceed a certain limit. Univalent 

 atoms obviously cannot build up a large 

 molecule by themselves, because when two 

 unite no more atomic affinities are left over. 

 The only apparent exceptions are where such 

 a binary compound of two univalent atoms 

 unites with water to form crystals, or where 

 two such binary compounds unite together 

 in a feeble way. But this is not atomic union 

 at all. It belongs to the molecular com- 

 binations described in the next chapter. 



If we next consider a divalent element 

 attempting to unite atomically to form large 

 groups, it becomes obvious that to form any 

 dynamic concatenation, or constellation, each 

 atom will have to unite with two others, and 

 hence no affinities are left over to enter into 

 similar relations with the other dissimilar 

 elements necessary to make up the molecule. 

 For example, a large number of oxygen atoms 

 might begin to bind together in interplay, 



