1917] on The Complexity of the Chemical Elements 121 



tricallj neutral state. Every atom being the seat of distinct opposite 

 charges, intensely localised, the state of electric neutrality can apply 

 only to a remote point outside it, remote in comparison with its own 

 diameter. "We are getting back to the conception of Berzelius, with 

 some possibihty of understanding it, that the atom of hydrogen, for 

 example, may be strongly electro-positive, and that of chlorine strongly 

 electro-negative, with regard to one another, and yet each may be 

 electrically neutral in the molar sense. Some day it may be possible 

 to map the electric field surrounding each of the ninety-two possible 

 types of atom, over distances comparable with the atomic diameter. 

 Then the study of chemical character Avould become a science in 

 Kelvin's sense, of something that could be reduced to a number. 

 But the mathematical conceptions and methods of attack used 

 in electrostatics for macroscopic distances are ill-suited for the 

 purposes of chemistry, which will have to develop methods of 

 its own. 



AVe have to face an apparent paradox that the greater the affinity 

 that binds together the material and electrical constituents of the 

 atom, the less is its combining power in the chemical sense. In 

 other words, the chemical affinity is in inverse ratio to the affinity of 

 matter for electrons. The helium atoms offer a very simple and 

 instructive case. Helium is non-valent and in the zero family, 

 possessing absolutely no power of chemical combination that can be 

 detected. Yet we know the atom possesses two electrons, for in 

 radioactive change it is expelled without them as the a-particle. The 

 discharge of electricity through it and positive-ray analysis show^ that 

 the electrons, or certainly one of them, are detachable by electric 

 agencies, although not by chemical agencies. One would expect 

 helium to act as a diad, forming helides analogous to oxides. 



Professor Armstrong for long advocated the view that these inert 

 gases really are endowed with such strong chemical affinities that 

 they are compounds that have never been decomposed. They cer- 

 tainly have such strong affinities for electrons tLat the atom, the 

 complex of the + ion and electrons, cannot be decomposed chemically. 

 Yet, in this case, w^here the affinity of the matter for the electron is 

 at a maximum, the chemical combining power is absent. 



These gases seem to furnish the nearest standard we have to 

 electric neutrality in the atomic sense. The negative charge of the 

 electrons exactly satisfies the positive charge of the matter, and the 

 atomic complex is chemically, because electrically, neutral. In 

 the case of the electro-positive elements, hydrogen and the alkali- 

 metals, one electron more than satisfies the positive charge on the 

 ion, and so long as the equality of opposite charges is not altered, 

 the electron tries to get away. In the case of the electro-negative 

 elements, such as the halogens, the negative charge, though equal 

 presumably to the positive, is not sufficient to neutralise the atom. 

 Hence these groups show strong mutual affinity, one having more 



