Classical resonance rule for predicting the stability/instability of fullerene molecules

This communication describes a novel criterion, hereafter called the one-th ird rule, which enables us to judge molecular stability/instability for car bon cages such as fullerene molecules. This rule is based on the concept th at the degree of orbital hybridization around each carbon atom (vertex, sit e) with three-valency can be expressed as a 3-tuple ( P-1, P-2, P-3), where P-i are Pauling bond orders around that carbon atom. By means of such 3-tu ples and the solid-geometrical concepts, all the carbon atoms of fullerene molecules can be classified as either stable or unstable. A given fullerene molecule is thus said to be either stable if it has stable carbon atoms on ly or unstable if it has at least one unstable carbon atom. The present pap er shows that the one-third rule which is applied to 6 isomers of C-60 and 3 isomers of C-70 is effective.