NO. II STRUCTURE OF THE ATOM PARSON 33 



required to make up the group of eight increases, because of the 

 increasing electrostatic strain involved; and so the order of inten- 

 sity is £. f > \; t > p f > V. > . If the intensity of the negative action 



of the atom of an element is to be judged by the readiness with which 

 it unites with Hydrogen or with the metals, as is reasonable, Nitrogen 

 and Phosphorus must be fairly weak in this respect, and Carbon and 

 Silicon can have very little tendency to combine negatively ; this is 

 just as theory here would lead us to expect. 



Further, this gradation in the tendency to form the group of eight 

 leads us to the conclusion that there must be, in the molecules of the 

 hydrides of these elements a kind of tautomerism or dynamical 

 equilibrium between the two possible modes of union, as follows : 



the proportion of polarized molecules increasing regularly from 

 CH 4 , where it is very small, to HF, in which it greatly predominates. 

 In view of the incessant vibrations of all molecules, this is mechanic- 

 ally a more likely condition than the statical one in which the 

 Carbon atom just does not, and the Nitrogen atom just does, succeed 

 in forming the group of eight. The constitutions of these molecules 

 are of fundamental importance in chemistry, for they are the four 

 typical molecules of the old type theory,' and three of them, viz., 

 NH 3 , OH 2 , and FH, typically represent almost all ionizing solvents ; 

 these three also differ from CH 4 , as we have seen, in that the 

 unpolarized tautomer contains a certain number (always even) of 

 valence magnetons that are free — that is, it is unsaturated. 



With regard to the intensity of the positive action of an atom (as 

 shown in its typical oxide), the increasing number of magnetons 

 that must be extracted from an atom in forming its typical oxide, as 

 we pass from group I to group VII, results in a decreasing stability 

 of that oxide, for electrostatic reasons. Hence we have the following 

 stability relations : 



B 2 3 >C0 2 >N 2 5 >[00 3 ] [F 2 7 ], 

 A1 2 3 Si0 2 >P 2 5 > SO s > C1 2 7 , 



Ti0 2 V 2 6 >Cr0 3 >Mn 2 7 , etc. 

 The progress from basicity to acidity in the hydroxides as we pass 

 from group I to group VII is a matter of the greatest interest, and 

 much light can be thrown upon it by considering the electrostatic 

 3 



