4i6 



NATURE 



[July 19, 1917 



must possess inertia inversely proportional to the 

 diameter of the sphere on which it is concentrated by 

 reason of the electromagnetic principles discovered by 

 Faraday, leading to the all-embracing monism that all 

 mass may be of electromagnetic origin. 



This put the coping-stone to the conclusion that the 

 elements as we apprehend them in ordinary matter are 

 always compounds. In the "free" state they are com- 

 pounds of the element in multiple atomic proportions 

 with the electron. The ions, which are the real chem- 

 ically uncombined atoms of matter, can no more exist 

 free in quantity than can the electrons. 



The compound may be individual as between the 

 atom and the electron, or it may be statistical, affect- 

 ing the total number merely of the opposite charges, 

 and the element presumably will be an insulator or 

 conductor of electricity accordingly. Analogously, with 

 compounds, the former condition applies to unionised 

 compounds, such as are met with in the domain of 

 organic chemistry, or ionised, as in the important 

 classes of inorganic compounds, the acids, bases, and 

 salts. Just as the chemist has long regarded the 

 union of hydrogen and chlorine as preceded by the 

 decomposition of the hydrogen and chlorine molecule, 

 so he should now further regard the union itself as a 

 decomposition of the hydrogen atom into the positive 

 ion and the negative electron and a combination of 

 the latter with the chlorine atom. 



One of the barriers to the proper understanding and 

 quantitative development of chemical character from 

 this basis is perhaps the conventional idea derived from 

 electrostatics that opposite electric charges neutralise 

 one another. In atomic electricity or chemistry, 

 though the equality of the opposite charges is a neces- 

 sary condition of existence, there is no such thing 

 as neutralisation or the electrically 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 possi- 

 bility 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 would 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. 



We have to face an apparent paradox that the greater 

 the affinity that binds together the material and elec- 

 trical constituents of the atom, the less is its combin- 

 ing power in the chemical sense. In other words, the 

 chemical affinity is in inverse ratio to the affinity of 

 matter for electrons. The helium atom offers a very 

 simple and instructive case. Helium is non-valent and 

 in the zero family, possessing absolutely no power of 

 chemical combination that cap be detected. Yet we 

 know the atom possesses two electrons, for in radio- 

 active 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 cer- 

 tainly 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. 



Prof. Armstrong for long advocated the view that 

 these inert gases really are endowed with such strong 

 chemical affinities that they are compounds that have 

 NO. 2490, VOL. 99] 



never been decomposed. They certainly have such 

 strong afiinities for electrons that the atom, the com- 

 plex of the + ion and electrons-, cannot be decomposed 

 chemically. Yet in this case, where 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 posi- 

 tive 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 and the other 

 less negative electricity than would make the system 

 atomically neutral like helium. The electron explains 

 well the merely numerical aspect of valency. But 

 chemical combining power itself seems to require the 

 idea that equal and opposite charges in the atomic 

 sense are only exactly equivalent in the case of the 

 inert gases. None of these ideas are now new, but 

 their consistent application to the study of chemical 

 compounds seems curiously to hang fire, as though 

 something were still lacking. 



It is so difficult for the chemist consistently to realise 

 that chemical affinity is due to a dissociating as well 

 as to a combining tendency, and is a differential effect. 

 There is only one affinity, probably, and it is the same 

 as that between oppositely charged spheres. But, 

 atomic charges being enormous, and the distances over 

 which they operate in chemical phenomena being 

 minute, this affinity is colossal, even in comparison 

 with chemical standards. What the chemist recog- 

 nises as affinity is due to relatively slight differ- 

 ences between the magnitude of the universal tendency 

 of the electron to combine with matter in the case of 

 the different atoms. Over all is the necessary condi- 

 tion that the opposite charges should be equivalent, 

 but this being satisfied, the individual atoms display 

 the tendencies inherent in their structure, some to lose, 

 others to gain electrons, in order, as we believe from 

 Sir Joseph Thomson's teaching, to accommodate the 

 number of electrons in the outermost ring to some 

 definite number. Chemical affinity needs that some 

 shall lose as well as others gain. Chemical union is 

 always preceded by a dissociation. The tendency to 

 combine, only, is specific to any particular atom, but 

 the energy and driving power of combination are due 

 to the universal attraction of the -f- for the — charge, 

 of matter for the electron. 



The Electrical Theory of Matter. 

 Another barrier that undoubtedly exists to the better 

 appreciation of the modern point of view, even among 

 those most willing to learn, is the confusion that 

 exists between the earlier and the present attempt 

 to explain the relation between matter and electricity. 

 We know negative electricity apart from matter as the 

 electron. We knov/ positive electricity apart from the 

 electron, the hydrogen ion, and the radiant helium 

 atom, or a-particle of radio-active change, for example, 

 and it is matter in the free, or electrically uncombined, 

 condition. Indeed, if you want to find matter free 

 and uncombined, the simple elementary particle of 

 matter in the sense of complexity being discussed, you 

 will go, paradoxically, to what the chemist terms a 

 compound rather than to that which he terms the free 

 element. If this compound is ionised completely it 

 : constitutes the nearest approach to matter in the free 



