Even though nitrogen in ammonia is in `sp^(3)` hybridization, the bond angle deviate form `109^(@)28`. Explain.

Explanation

In `NH_(3)` molecule, three `sp^(3)` hybrid orbitals contain bond pairs and one `sp^(3)` hybrid orbital contains a lone pair of electrons. There will be repulsions between the lone pair and bond pair electrons. These are stronger than bp-bp repulsions. (I.p-b.p `gt` b.p - b.p). So the bond pairs are pused closer together angle. The molecule assumes a pyramidal shape.