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valence-shell-electron-pair repulsion theory
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Diagram showing VSEPR electron pair arrangements and their corresponding molecular shapes, including linear, trigonal planar, angular, tetrahedral, trigonal pyramidal, trigonal bipyramidal, seesaw, T-shaped, octahedral, square pyramidal, and square planar geometries. Each arrangement is illustrated with red lines and electron pairs.
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valence-shell-electron-pair repulsion theory

Also known as: VSEPR theory
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Diagram showing VSEPR electron pair arrangements and their corresponding molecular shapes, including linear, trigonal planar, angular, tetrahedral, trigonal pyramidal, trigonal bipyramidal, seesaw, T-shaped, octahedral, square pyramidal, and square planar geometries. Each arrangement is illustrated with red lines and electron pairs.
electron pairs and molecular shape VSEPR electron pair arrangements and associated molecular shapes.

Valence-shell electron-pair repulsion (VSEPR) theory is a model used to predict the geometric arrangement of atoms in molecules. It's based on the principle that electron pairs in the valence shell of a central atom repel each other and will arrange themselves as far apart as possible to minimize these repulsions. This arrangement dictates the molecule's shape.12

Key points of VSEPR theory:
* Electron Pairs: Both bonding pairs (shared between atoms) and lone pairs (unshared) around a central atom influence molecular shape.12
* Repulsion Minimization: The molecule adopts a shape that minimizes the repulsion between these electron pairs.12
* Predicting Shape: By considering the number of bonding and lone pairs, VSEPR theory can predict shapes like tetrahedral (e.g., methane, CH4), angular (e.g., water, H2O), or trigonal pyramidal (e.g., ammonia, NH3).12

While simple and effective, VSEPR theory has limitations, such as not predicting exact bond angles or lengths and relying on somewhat vague concepts regarding lone pair repulsion.1

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2 Britannica Sources
  1. chemical bonding - Limitations of the VSEPR model
  2. chemical bonding - Applying VSEPR theory to simple molecules

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