THE ELECTRON 97 



also atoms which we recognize to be helium. Helium 

 is a light monatomic gas, twice as heavy as diatomic 

 hydrogen. Its atom consists of a nucleus and two 

 electrons. 



Since such an atom is shot off from radium it ap- 

 pears to mean that the nucleus of the radium atom 

 contains, or possibly is made up of, helium atoms. It is 

 also possible that these helium atoms are themselves 

 made up of hydrogen atoms. If this is the case, the 

 nucleus of each helium atom should consist of four 

 nuclei, like that of the hydrogen atom, and two elec- 

 trons. This helium nucleus would then require two 

 external electrons in order to be neutral. That the 

 helium atom has two electrons external to the nucleus, 

 we know, but we are as yet in the dark as to whether 

 or not the nucleus is formed as suggested above. The 

 point to be noted is that, even though scientists are not 

 yet able to speak definitely of the composition of the 

 nucleus, there is sufficient evidence to warrant our 

 bearing in mind the possibility that the nuclei of all 

 the atoms may some day be found to be formed by the 

 combination of electrons and a number of positive ele- 

 mental charges l all just like the positive nucleus of the 

 hydrogen atom. 



1 If we use the term "electron" to mean an element of electricity 

 we must distinguish between this positive electron and the negative 

 electron with which we have previously dealt. This is the practice 

 of such pioneers in electron physics as J. J. Thomson, Millikan, 

 and Rutherford. Unfortunately the Century Dictionary has not re- 

 corded this usage. It happens, however, that our further discus- 

 sions concern only the negative electron, and for convenience we 

 shall continue to use the term without qualification to represent 

 the elementary negative charge. 

 H 



