-874 



Mr. L. St. C. Brouehall on 



making the atom unstable. Tins is the case of the Argon 

 and Xenon atoms. 



In the case of the inert gases the outer shell is always 

 complete and there is no tendency to acquire other electrons; 

 their valency is therefore zero. Ail the other elements have 

 the outer shell incomplete, and the valency is given by the 

 number of electrons which must be gained or lost in order 

 to produce the stable structure peculiar to the inert gases. 



The Boron atom with an atomic number of 5 consists of a 

 positive nucleus ; then there are two electrons corresponding 

 to the Helium atom, and finally a ring of three electrons in 

 the shell corresponding to the Neon shell. 



The diameter of the atom should therefore be the same as 

 that of the Neon atom, namely 2*58 x 10" 8 cm. These 

 figures therefore give considerable support to this interesting 

 theory ; but it must be remembered that only when the 

 atomic diameter is calculated from "&" of Van der Waals' 

 equation is this constant increase in diameter to be found. 



Now, knowing the ratio of the diameter of one shell to 

 that of the next, one can obtain some further atomic values. 



The element Beryllium has an atomic number " 4," 

 therefore the electrons are four in number, and so the atom 

 can be represented by a plain figure as the electrons are 

 distributed between two shells. 



Ficr. 1. 



BfLK^ 



Now all the electrons have the same charge, which w« 

 will call " <?," and we will further call the respective electrons 

 e u e 2 , <? 3 , and <? 4 . Further, let us give the positive nucleus a 



