Valence bond alternatives to double bonds and triple bonds

The results of ab initio valence bond calculations for dinitrogen show that resonance between the valence bond structures [graphic omitted] and [graphic omitted] with electron-pair σ bonds and one-electron π bonds, generates a lower energy than does the triple-bond structure [graphic omitted]N ≡ N[graphic omitted] with Coulson–Fischer-type wavefunctions for the two π bonds. When the wavefunctions for these two sets of structures are expressed as linear combinations of wavefunctions for nine canonical Lewis structures, it is found that the triple-bond structure overestimates the importance of the highly polar canonical structures [graphic omitted] and [graphic omitted], and this is the origin of the higher energy for the triple-bond structure.