* 
740 The Philippine Journal of Science 
surrounded by groups of four, in which two electrons are shared 
between the two groups. The reason for expressing the case in 
these words is that in nitric oxide, : -N.O- : , the seven kernel 
-O- 
electrons can be accounted for as two groups of four in which 
one electron is shared. 
SUMMARY 
1. Reasons are given for considering that chlorine dioxide con- 
tains a three-electron bond. 
2. The electron binding strength of atoms and its variation 
with the covalence is discussed in connection with the tendency 
to share electrons. 
3. In conformity with older usage the single-electron bond is 
called the half bond and its importance is indicated. 
