Izomers of triatomic molecules ABX

For triatomic molecules ABX, consisting of atoms with s- and p-electrons, in particular CB2, BC2, B2O, BNC, BOAl, BOHal (Hal=F, Cl, Br, I), the problem of relative stability of isomers, differing in relative position of atoms, is studied theoretically. The consideration is carried out in the framework of perturbation theory with molecules of (AAA)sup(+-q) type, as non-perturbed system. It is ascertained, that the relative stability of the isomers is determined by total numbr (N) of valence p-electrons in the molecule and position of atoms A, B, X on the scale of orbital electronegativities. At N < 9 isomers with the most electronegative atom in the centre are the most stable ones. At N > 9 isomers with the most electropositive atom in the centre are stabilized. The analysis results are used to interpret the data of nonempirical quantum-chemical caculations