This answer is not correct. Ammonia is a has a dipole moment because there is a reasonable difference in the electronegativity of nitrogen and the electronegativity of hydrogen...these bonds are polar...and it has a pyramidal molecular geometry...tetrahedral electron-pair geometry. The nitrogen atom is sp³ hybridized (tetrahedral) because the nitrogen atom is bound to three hydrogen atoms and has one pair of non-bonded electrons. Remember that electron pairs occupy space and repel other electron pairs and atoms. Therefore they must be in hybrid orbitals.