102 ORIGIN AND NATURE OF LIFE 



but both affinities would be involved in 

 holding them in such relations, and so none 

 would be left over for attaching any other 

 element. Hence the whole group could be 

 oxygen, and oxygen only ; no compound could 

 be formed. 



The lowest valency at which such dynamic 

 grouping of a considerable number of atoms 

 could occur is that of the trivalent atom, 

 where after the unions of the trivalent atoms 

 one valency would be left upon each for union 

 with the dissimilar atoms or groups. Although 

 this is feasible there are objections from the 

 point of view of stability of the system, 

 for while in process of building up in the 

 tetrad grouping there are two affinities left 

 over on each atom which can interplay with 

 each other and hold each other balanced in 

 equilibrium, until other atoms or atomic 

 groups of a dissimilar character present 

 themselves ; in the case of the triad, only 

 one unbalanced activity, or valency, is left 

 over on each atom, and this is an exceedingly 

 unstable situation, so that the system breaks 

 up. Also it is questionable whether true 

 trivalent atoms exist at all in nature because 

 they are themselves so unstable. The elements 

 of the phosphorus group, namely, nitrogen, 

 phosphorus, arsenic, and antimony, which 



