VSEPR Theory
The model that predicts molecular shape by arranging valence electron pairs around a central atom so their mutual repulsion is minimised.
Formula / equation
AXₘEₙ notation
Unit
Dimensionless
In depth
Repulsion decreases in the order lone pair–lone pair, lone pair–bond pair, bond pair–bond pair, so lone pairs take the roomiest positions and squeeze the remaining bond angles. Multiple bonds count as a single electron domain. The theory is simple yet predicts the geometry of most main-group molecules correctly.
Examples in the real world
SF₄ adopts a see-saw shape because its lone pair takes an equatorial site; XeF₄ is square planar with two axial lone pairs.