Why ammonia shows sp3 hybridization?

Answer 1

In ammonia the N atom because it is period 2 can only realistically hybridize as sp, sp2 or sp3. The geometry is trigonal pyramidal, so sp3 hybridisation is the best fit, the other options would not fit the geometry.

In actuality the bond angle of 1070 shows that as the angle is closer to 90 than in "true" sp3 (1090)the bonds have slightly more p character (porbitals are at 900), leaving the lone pair with slightly more s character..

Answer 2

Ammonia (NH3) shows sp3 hybridization because the nitrogen atom has one 2s orbital and three 2p orbitals that undergo hybridization to form four equivalent sp3 hybrid orbitals. These hybrid orbitals allow the nitrogen atom to form four equivalent sigma bonds with the three hydrogen atoms and the lone pair of electrons.