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According to the valence bond theory, Electrons in a molecule occupy atomic orbitals rather than molecular orbitals. The atomic orbitals overlap on the bond formation and the larger the overlap the stronger the bond.

Applications of Valence Bond Theory

• The maximum overlap condition which is described by the valence bond theory can explain the formation of covalent bonds in several molecules.
• This is one of its most important applications. For example, the difference in the length and strength of the chemical bonds in H₂ and F₂ molecules can be explained by the difference in the overlapping orbitals in these molecules.
• The covalent bond in an HF molecule is formed from the overlap of the 1s orbital of the hydrogen atom and a 2p orbital belonging to the fluorine atom, which is explained by the valence bond theory.

Limitations of Valence Bond Theory

The shortcomings of the valence bond theory include

• Failure to explain the tetravalency exhibited by carbon
• No insight offered on the energies of the electrons.
• The theory assumes that electrons are localized in specific areas.
• It does not give a quantitative interpretation of the thermodynamic or kinetic stabilities of coordination compounds.
• No distinction between weak and strong ligands.
• No explanation for the colour exhibited by coordination compounds.