VSEPR theory

Example of bent electron arrangement (water molecule). Shows location of unpaired electrons, bonded atoms, and bond angles. The bond angle for water is 104.5°.

Valence shell electron pair repulsion (VSEPR) theory (/ˈvɛspər, vəˈsɛpər/ VESP-ər,^[1]^: 410 və-SEP-ər^[2]) is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms.^[3] It is also named the Gillespie-Nyholm theory after its two main developers, Ronald Gillespie and Ronald Nyholm.

The premise of VSEPR is that the valence electron pairs surrounding an atom tend to repel each other. The greater the repulsion, the higher in energy (less stable) the molecule is. Therefore, the VSEPR-predicted molecular geometry of a molecule is the one that has as little of this repulsion as possible. Gillespie has emphasized that the electron-electron repulsion due to the Pauli exclusion principle is more important in determining molecular geometry than the electrostatic repulsion.^[4]

The insights of VSEPR theory are derived from topological analysis of the electron density of molecules. Such quantum chemical topology (QCT) methods include the electron localization function (ELF) and the quantum theory of atoms in molecules (AIM or QTAIM).^[4]^[5]

^ Cite error: The named reference Petrucci was invoked but never defined (see the help page).
^ Stoker, H. Stephen (2009). General, Organic, and Biological Chemistry. Cengage Learning. p. 119. ISBN 978-0-547-15281-3.
^ Jolly, W. L. (1984). Modern Inorganic Chemistry. McGraw-Hill. pp. 77–90. ISBN 978-0-07-032760-3.
^ ^a ^b Gillespie, R. J. (2008). "Fifty years of the VSEPR model". Coord. Chem. Rev. 252 (12–14): 1315–1327. doi:10.1016/j.ccr.2007.07.007.
^ Bader, Richard F. W.; Gillespie, Ronald J.; MacDougall, Preston J. (1988). "A physical basis for the VSEPR model of molecular geometry". J. Am. Chem. Soc. 110 (22): 7329–7336. doi:10.1021/ja00230a009.

[Petrucci-1] Cite error: The named reference Petrucci was invoked but never defined (see the help page).

[H2009-2] Stoker, H. Stephen (2009). General, Organic, and Biological Chemistry. Cengage Learning. p. 119. ISBN 978-0-547-15281-3.

[Jolly-3] Jolly, W. L. (1984). Modern Inorganic Chemistry. McGraw-Hill. pp. 77–90. ISBN 978-0-07-032760-3.

[Fiftyyears-4] Gillespie, R. J. (2008). "Fifty years of the VSEPR model". Coord. Chem. Rev. 252 (12–14): 1315–1327. doi:10.1016/j.ccr.2007.07.007.

[5] Bader, Richard F. W.; Gillespie, Ronald J.; MacDougall, Preston J. (1988). "A physical basis for the VSEPR model of molecular geometry". J. Am. Chem. Soc. 110 (22): 7329–7336. doi:10.1021/ja00230a009.

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