the Molecule and Chemical Combination. 



531 



Thus we see that a combination of this type, not deter- 

 mined in any way by considerations' of valency, might be as 

 stable and as saturated as the combination of atoms in the 

 molecule of an elementary gas. One condition for the 

 existence of compounds of this type is that the sum of the 

 electrons on the two atoms should be greater than 8. Thus 

 we should not expect, what perhaps on the ordinary theory 

 of valency we might expect, that the existence of CO implied 

 the independent existence of CrJ 25 f° r this would have only 

 6 disposable electrons, and as these are insufficient to pro- 

 duce a completely saturated layer, they could not form a 

 completely saturated compound. 



It is important to point out that we distinguish between 

 the molecule of carbon monoxide and that of the car bony 1 

 radicle CO. In the latter we suppose that two out of the four 

 electrons of the carbon atom have gone to unite it with the 

 oxygen and to make up the 8 required to form the cell 

 round the oxygen atom, while the other two are free to join 

 up with other electrons, so that while the molecule of 

 CO is represented by fig. 9 that of the carbonyl radicle 

 is represented by 



Fio-. 10. 



The constitution of C0 2 is I think best regarded as the 

 union of an oxygen atom with the two electrons a 3 # 4 of the 

 carbonyl radicle and having the configuration represented 

 by fig. 11, where the 16 electrons are arranged in 3 cells of 



Fio-. 11. 



8 round each of the atoms, each cell having 1 electrons in 

 common with its next neighbour, these forming a double 

 bond between each pair of adjacent atoms. To simplify the 

 diagram the cells are represented as cubes. 



It must be acknowledged that there are some compounds 



