The Chemical Bonds in Valence Bond Theory

This chapter involves a panoramic description of bonding. Among single bonds, we demonstrate the existence of charge-shift bonds (CSBs) wherein bonding originates mostly/only from the covalent–ionic resonance energy (e.g., F–F, Mn–Mn, and hypervalent molecules, e.g., XeF 2 ). The resonance energy is quantifiable from experimental data. For multiple bonds we derive hybridization and analyze multiple bonding in C 2 and 3 O 2 . An effective methodology of minimizing the number of VB structures reveals that the dominant structure of C 2 displays a quadruple CC bond. Dioxygen, which is persistent and life-sustaining, is shown to be stabilized by CSB of two cooperative π-3-electron bonds. Subsequently we discuss the roles of π vs. σ in the geometry of benzene, acetylene, ethene, vs. their Si-based analogs. This is followed by consideration of triplet-pair bonds (TPBs) in n +1 M n clusters (M-univalent), which possess only parallel spins, and are nevertheless bonded due to the resonance interactions that stabilize the repulsive elementary structure (wherein all spins are up).