DIAMONDS — LOGIE 



369 



2P 

 2 S 



1 S 



Figure 4. 



(G.2) 

 (5,1) 

 (5.0) 

 (4.3) 

 (5,2) 

 (6,1) 

 (6,0) 



(4,2) 

 (5.1) 

 (5,0) 



(3 2 

 (4,'l 

 (4,0) 



(3,1) 

 (3,0) 



(2,1) 

 (2,0) 



(1.0) 



respective energies are shown in figure 4. The orbit closest to the 

 nucleus can have two electrons in it ; then there is a fairly large energy 

 gap and we come to a pair of orbits which together are known as the 

 Z-shell and which can accommodate eight electrons. Again there is 

 a fairly wide energy gap before we come to the next group of possible 

 orbits and so on. The two important points to appreciate at this stage 

 are, first, that only certain energy levels are possible and between 

 these levels there are energy values which are "forbidden," and second, 

 that the closer an electron is to the nucleus, the lower is its energy. 



As the carbon atoms are brought together to form a crystal, one can 

 imagine the competition for the possession of electrons to fill the 

 shells. An elegant compromise is reached. Each carbon atom takes 

 four neighbors and shares an electron with each of them. A con- 

 tribution of one electron from each atom will be found along the line 

 joining two of them together. Every atom is now surrounded by 



