784 



Sir J. J. Thomson on the 



force which, since the hydrogen atom only contains one 

 free corpuscle, is the only condition that has to be fulfilled. 

 On the usual theory of valency, H 3 is not possible as a 

 valency compound. Again, taking silver as monatomic, 

 Ag CI, Ag Ci 2 , or indeed Ag Cl„ would all be possible 

 valency compounds, though they would not on the older 

 theory. The difference between the two theories is specially 

 noticeable in the case of ring or chain compounds, and it is 

 interesting to write down the simplest formula for benzene 

 from this point of view ; it is 



It will be seen that this benzene ring is entirely symme- 

 trical, and that the linkage between the carbon atoms is not 

 the same as that in 



ethane 



ethylene 



or acetylene 



0* 







c 







c 



^0 



