Select shape
What is VSEPR?
Valence Shell Electron Pair Repulsion theory predicts molecular shape. Electron pairs — both bond pairs and lone pairs — repel each other and arrange themselves as far apart as possible.
Lone pair repulsion
Lone pairs repel more strongly than bond pairs because they are held closer to the nucleus. Each lone pair compresses the bond angles by about 2–2.5° compared to the ideal geometry.
Naming the shape
The shape name describes only the arrangement of atoms, not lone pairs. A molecule with 4 electron pairs and 1 lone pair is trigonal pyramidal — not tetrahedral — because we ignore the lone pair when naming.
5 electron pairs
In trigonal bipyramidal geometry, lone pairs preferentially occupy equatorial positions (120° apart) because axial positions have more repulsion (3 × 90° interactions vs 2 × 90°).