VSEPR Theory & Molecular Shapes

Valence Shell Electron Pair Repulsion, or VSEPR, theory predicts the three-dimensional shape of a molecule from the arrangement of electron domains around its central atom. The central idea is simple: electron pairs in the valence shell repel one another and therefore spread out to be as far apart as possible, minimizing repulsion and fixing the geometry. An electron domain is any region of electron density, whether a single bond, a double bond, a triple bond, or a lone pair. Multiple bonds count as a single domain because the electrons occupy one region of space.

To apply VSEPR, first draw the Lewis structure, then count the electron domains around the central atom. The number of domains sets the electron-domain geometry, and the number of those that are bonding versus lone pairs sets the