In the compound NH3 ammonia , the nitrogen atom is sp3 hybridized. To determine the hybridization, we can look at the number of electron domains regions of electron density around the nitrogen atom. In NH3, nitrogen has three single bonds with three hydrogen atoms and one lone pair of electrons. This gives a total of four electron domains. When there are four electron domains, the hybridization is sp3, which means that one s orbital and three p orbitals are hybridized to form four sp3 hybrid orbitals.