On the nature of the chemical bond in valence bond theory.

This Perspective outlines a panoramic description of the nature of the chemical bond according to valence bond theory. It describes single bonds and demonstrates the existence of a "forgotten family" of charge-shift bonds (CSBs) in which the entire/most of the bond energy arises from the resonance between the covalent and ionic structures of the bond. Many of the CSBs are homonuclear bonds. Hypervalent molecules (e.g., XeF