532 Sir J. J. Thomson on the Structure of 



which we might expect from this point of view and of 

 which we have no evidence : for example, the molecule NF 

 contains 12 electrons like the oxygen molecule, and we might 

 expect that a configuration of electrons resembling with 

 some distortion that of 2 might give a stable molecule 

 with properties somewhat similar to 2 . So far as I 

 am aware, no such compound has ever been detected or 

 suspected. It must be remembered that the molecule N 2 

 which forms the type for CO is singularly inert : if a sub- 

 stance formed on the model of 2 were to have more 

 energetic chemical qualities than those of its prototype, it 

 might enter into combination so readily as to escape observa- 

 tion in the free state. 



We have, however, in the compounds of nitrogen and 

 oxygen probably other examples of this type of molecule. 

 The molecule of NO contains eleven. electrons : if we take 

 eight of these to form the outer cell we are left with three 

 which, by taking up positions at the corners of a triangle 

 in a plane between the atoms of nitrogen and oxygen, may 

 help to keep these atoms together. The molecule of nitrogen 

 monoxide is not the only form in which the combination NO 

 occurs; besides this, there is the radicle NO, and just as we 

 supposed the carbonyl radicle to have a different configura- 

 tion from that of the molecule, so we suppose that the radicle 

 NO has a configuration where 8 electrons form a cell of 

 8 round the oxygen, while there is a cell of 7 round the 

 nitrogen, the two cells having 4 electrons in common. 

 Thus the cell round the nitrogen is unsaturated and the 

 combination will act like a seven-electron atom, i. e. be 

 univalent. 



The three electrons left over from the five nitrogen 

 electrons after tw<o have been used to saturate the cell round 

 the oxygen atom might bind three hydrogen ions, and thus 

 it is possible that under certain circumstances the radicle 

 might act as if its valency were three. 



The view we have taken of the structure of molecules 

 is consistent with the existence of many compounds which 

 violate the ordinary valency conditions. According to this 

 view a molecule would be saturated, if the disposable 

 electrons — i. e., those which before combination occupied 

 the outer layers of the atoms which make up the molecule — 

 can be arranged in a number of connected cells, each cell 

 containing 8 electrons. The cells must be numerous enough 

 for the core of each atom which possesses four or more 

 electrons to be placed inside a separate cell. The reason 



