CHEM 121 glossary

Hybrid orbital

One of the equivalent orbitals formed when an atom mixes its valence s and p (and d) atomic orbitals; the number of hybrids equals the number of atomic orbitals mixed. Each has one large lobe pointing toward a bonded atom or a lone pair, and hybrids form σ bonds or hold lone pairs, never π bonds.

One $s$ + three $p$ orbitals give four $sp^3$ hybrids.

Example

Mixing one $2s$ and two $2p$ orbitals gives three $sp^2$ hybrids at 120° and leaves one $2p$ unmixed. In $\ce{BF3}$ each boron $sp^2$ hybrid overlaps an F orbital to form a B–F σ bond, and the leftover $2p$ on boron is empty.