Valence bond theory, primarily the work of Linus Pauling regarded bonding as characterized by the overlap of atomic or hybrid orbitals of individual atoms.
Although VB theory was the principal way in which chemist visualized coordination compounds until the 1950s, it has fallen into disfavour due to its inability to account for various magnetic, electronic and spectroscopic properties of these compounds.
Defects of Valence bond theory
- The main defect of the simple Valence bond theory lies in its failure
- To include the anti bonding molecular orbitals produced during complex formation.
- It fails to offer an explanation for the striking colors of many complexes, which arise from their selective absorption of light of only certain wavelengths
Another common case in which VB theory will struggle is in the prediction of bonding in transition metal compounds as these undergo different types of bonding from most non-metals. VSEPR also fails when looking at transition metals due to the change from VB theory to MO theory.