756 Application of Electron Theory of Chemistry to Solids. 



Thus the force tending to increase the displacement is 

 greater than that tending to diminish it, and so the equi- 

 librium is unstable. 



It follows from this result that the equilibrium of a long- 

 chain of carbon atoms alone must be unstable. 



With atoms such as those of oxygen, which can have 

 positive charges amounting to six units, a chain such as 

 is shown in plan in fig. 6, where the electrons are at the 

 corners of cubes placed so that each cube has an edge 

 in common with its nearest neighbour, would satisfy the 



Fig. 6. 



condition of having six electrons for each atom. An investi- 

 gation similar to that just given shows, however, that the 

 arrangement would be unstable. This is in accordance with 

 experience, as long chains of oxygen are exceedingly unstable. 

 A chain which I find to be just stable as far as the displace- 

 ment of electrons is concerned is that where doubly charged 

 atoms and electrons are arranged in the way shown in fig. 7* 



Fi< 



A 



V 



E 



/ 



The atoms A are arranged at equal intervals along a 

 straight line. The electrons are arranged in pairs, the 

 line joining the constituents of a pair being at right angles 

 to AA. Each pair is at right angles to its nearest neighbour. 

 Each atom is thus at the centre of a regular tetrahedron 

 formed by the elecirons which are its next nearest neighbours. 

 This arrangement is stable if the atoms are fixed ; and the 

 stability when the atoms are free to move can be insured by 

 giving a suitable value to the force between two positively 

 charged atoms. 



If the radicle CH 2 be regarded as equivalent to an atom of 

 a divalent element with two disposable electrons, then by the 

 preceding result we might expect to get long chains of CH 2 



