Five and six domains

Central atoms from period 3 and below, such as S, Cl and Xe, can have five or six electron domains. Five domains form a trigonal bipyramid: three equatorial positions 120° apart round the middle, and two axial positions above and below, at 90° to the equator. Six domains form an octahedron, where every neighbouring position is 90° away.

Contacts at 90° are the strongest repulsions. Lone pairs settle where they make the fewest 90° contacts. Lone pair–lone pair contacts are avoided first, then lone pair–bond contacts.