Recent advances in simple valence‐bond theory and the theory of hybrid bond orbitals

Abstract The history of important developments in the theory of hybrid bond orbitals and its application in valence‐bond theory is reviewed. One of the salient points, the bond strength of a hybrid orbital, is defined as the value of the angular part of the orbital along the bond direction. Characteristic bond angles corresponding to maxima in the bond strength are presented for various basis sets. In order to alleviate computational difficulties in determining the bond strength for complex systems, an approximation to it, the pair‐defect‐sum approximation, is described. The results of an exhaustive test of the validity of this approximation are presented. Applicaitions of these ideas to coordinate chemistry are provided. Finally, the case is made for the continued viability of valence‐bond theory in this age of omnipresent computer terminals.