CHEM 121 glossary

Hybridization

Mixing an atom's valence s and p (and sometimes d) orbitals into the same number of equivalent hybrid orbitals, which point toward the electron domains predicted by VSEPR. It is assigned from the steric number: 2 → $sp$ , 3 → $sp^2$ , 4 → $sp^3$ , 5 → $sp^3d$ , 6 → $sp^3d^2$ .

\ce{NH3}

: four domains (three bonds, one lone pair), so N is

sp^3

Example

N in $\ce{NH3}$ has 3 bonded atoms + 1 lone pair = steric number 4, so it is $sp^3$ : three hybrids bond to H and the fourth holds the lone pair. Each carbon in benzene has 3 domains, so it is $sp^2$ .