The Valence of the Argon Group, Etc. 341 



the molecule, and thus split the valence up; or that there are 

 partial valences in the sense of Kauffmann, 1 it seems to me 

 that we might as well abandon the whole valence idea. It 

 entirely loses its usefulness. Again our structural formulas 

 become so indefinite, if the valences are regarded as split up, 

 as to be nearly useless. The explanation which I sought 

 was one which would explain why we appear to have frac- 

 tional valences in this case, but really do not have them. 

 That my first explanation was wrong, was indicated by the 

 uniformity with which the valence increases from helium to 

 xenon. The deviation, too, from uni valency in the case of 

 neon is so great that it lies outside the limits of error. The 

 critical pressure would need to be 14 atmospheres instead of 

 that recorded of 29 atmospheres, in order that neon should 

 have one valence to each molecule. The uncertainty of the 

 critical pressure is far less than this. 



I believe the reason that the average number of valences 

 is a fraction in these gases is as follows: All of them are in 

 reality zero valent, so fas ar their chief valences are concerned, 

 but like many, if not all, other elements, they have the power 

 of opening up two residual valences. By their residual 

 valences, therefore, they are all bivalent. These two valences, 

 like most, or all, other residual valences, are of opposite 

 electrical sign, one being positive, the other negative. Not 

 all the atoms have these residual valences open at the same 

 instant, but always some of the atoms have them closed. The 

 molecular cohesion, as I have already pointed out, is not 

 influenced by these valences when they are in a closed or 

 reserve state, or, we might say, withdrawn within the atom; 

 it is only affected by the valences actually extending between 

 atoms, or open and in a state in which they may combine. 

 In xenon nearly all the atoms, or at any rate, 90 percent of 

 them, have the valences open, and the average valence per 

 atom, or molecule, is, therefore, 1.80-1.95; in krypton about 

 65 percent of the atom have open valences, and 35 percent 

 are closed, so that the average valence is about 1.30; in argon, 



1 Kauffmann: Ber. chem. Ges. Berlin, 41, 4404 (1908). 



