122 Professor Frederick Soddy [May 18, 



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 coml)ining 

 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 recognises as affinity is due to relatively slight 

 differences 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 condition 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 outer- 

 most 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 com- 

 bination is the universal attraction of the + for the - change, of 

 matter for the electron. 



The Electrical Theory of Matter. 



Another barrier that undoubtedly exists to the better apprecia- 

 tion 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. AVe 

 know negative electricity apart from matter as the electron. AVe 

 know positive electricity apart from the electron, the hydrogen ion 

 and the radiant helium atom or a-particle of radioactive change for 

 example, and it is matter in the free or electrically uncombined con- 

 dition. 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 lie terms the free element. 

 If this compound is ionised completely it constitutes the nearest 

 approach to matter in the free state. Thus all acids owe their 

 common acidic quality to really free hydrogen, the hydrogen' ion, a 



