Which theory states that bonds form through the spatial overlap of orbitals containing valence electrons?

• A. Valence-bond theory
• B. Molecular orbital theory
• C. VSEPR theory
• D. Hybridization theory

Answer: (A)

Bonds form when valence atomic orbitals from adjacent atoms spatially overlap, allowing a pair of electrons to be shared and creating a localized bond between the nuclei. This idea is the essence of valence-bond theory: the strength and type of bond come from how these orbitals overlap. Direct end-to-end overlap of orbitals between two atoms produces a sigma bond, while sideways overlap of p orbitals gives a pi bond, and multiple overlaps explain single, double, or triple bonds in a localized picture. Other theories describe bonding differently: molecular orbital theory treats electrons as occupying molecular orbitals that extend over the entire molecule rather than just between two overlapping orbitals; VSEPR explains molecular shapes from repulsion between electron pairs; hybridization theory describes mixing of atomic orbitals to form new, geometry-suited hybrids, often used within the valence-bond framework but not by itself defining bond formation through orbital overlap.