How did Linus Pauling’s valence-bond method differ from the molecular-orbital method?

Linus Pauling was a primary architect of valence bond theory, which interprets chemical bonding through the hybridization of atomic orbitals on individual atoms to form localized bonds. In this framework, bonds are viewed as the overlap of specific orbitals, making it highly effective for organic chemistry and understanding properties associated with functional groups.12

In contrast, the molecular orbital (MO) method describes electrons as being delocalized over all the nuclei of a molecule. While valence bond theory focuses on localized regions, MO theory is better suited for describing properties involving delocalization, such as the spectroscopic behavior of molecules.23

Although their formulations differ, both are quantum mechanical approximations of electronic structure. Valence bond theory is often favored for its intuitive link to individual bonds and molecular geometry, whereas MO theory is more amenable to computational implementation and provides a superior explanation for phenomena like the absorption of light, which involves antibonding orbitals not typically addressed in simple valence bond models.231