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Valence shell electron pair repulsion (VSEPR) theory (/ ˈ v ɛ s p ər, v ə ˈ s ɛ p ər / 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]
Valence shell electron pair repulsion (VSEPR) theory predicts molecule geometry. [11] [12] VSEPR predicts molecular geometry to take the configuration that allows electron pairs to be most spaced out. [11] [12] This electron distance maximization happens to achieve the most stable electron distribution.
It enables prediction and explication of molecular geometries that are not necessarily satisfactorily or even correctly explained by semi-empirical theories such as Walsh diagrams, atomic state hybridization, valence shell electron pair repulsion (VSEPR), softness-hardness-based models, aromaticity and antiaromaticity, hyperconjugation, etc. [1]
Thus, the number of electrons in lone pairs plus the number of electrons in bonds equals the number of valence electrons around an atom. Lone pair is a concept used in valence shell electron pair repulsion theory (VSEPR theory) which explains the shapes of molecules. They are also referred to in the chemistry of Lewis acids and bases. However ...
This shape is found when there are four bonds all on one central atom, with no extra unshared electron pairs. In accordance with the VSEPR (valence-shell electron pair repulsion theory), the bond angles between the electron bonds are arccos(− 1 / 3 ) = 109.47°. For example, methane (CH 4) is a tetrahedral molecule.
This represents the conversion of a lone pair of electrons into a bonding pair, which adds two electrons to the former atom's valence shell while leaving the latter's electron count unchanged. In the preceding steps, if there are not enough electrons to fill the valence shells of all atoms, preference is given to those atoms whose ...
According to the VSEPR model (Valence Shell Electron Pair Repulsion model), linear geometry occurs at central atoms with two bonded atoms and zero or three lone pairs (AX 2 or AX 2 E 3) in the AXE notation.
Gillespie did extensive work on expanding the idea of the Valence Shell Electron Pair Repulsion (VSEPR) model of Molecular Geometry, which he developed with Ronald Nyholm (and thus is also known as the Gillespie-Nyholm theory), and setting the rules for assigning numbers.