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valence bond theory
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valence bond theory

chemistry
Also known as: VB theory
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Valence bond theory is a chemical theory that explains how atoms bond together to form molecules. It was developed in the 1930s by scientists like Walter Heitler, Fritz London, John Slater, and Linus Pauling.1

The core idea of valence bond theory is that a chemical bond forms when atomic orbitals from different atoms overlap. The electrons within these overlapping orbitals then pair up, holding the atoms together. This overlap creates a region of increased electron density between the nuclei, which lowers the molecule's energy and stabilizes the bond.1

A key concept within valence bond theory is the "promotion of electrons." This explains how an atom, like carbon, can form more bonds than its basic electron configuration might suggest. For example, carbon typically has two valence electrons, but in molecules like methane (CH4), it forms four bonds. Valence bond theory explains this by proposing that an electron can be temporarily "promoted" to a higher energy orbital, allowing for the formation of additional bonds, which ultimately results in a more stable molecule.1

While valence bond theory is useful for understanding individual bonds, especially in organic chemistry, it has limitations. Another theory, molecular orbital theory, is often preferred for quantitative calculations and understanding properties that involve the delocalization of electrons across the entire molecule.2

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
5 Britannica Sources
  1. valence
  2. chemical bonding - Promotion of electrons
  3. chemical bonding - Limitations of the VSEPR model
  4. chemical bonding - Comparison of the VB and MO theories
  5. chemical bonding - Molecular orbitals of period-2 diatomic molecules

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