Question

Although geometries of NH₃ and H₂O molecules are distorted tetrahedral, bond angle in water is less than that of ammonia. Discuss.

Answer 1

Due to greater lone pair-bond pair repulsion, the HNH angle is slightly less than the tetrahedral angle. The actual HNH angle in NH₃, is 107°.

In H₂O,  greater repulsion between lone-pair-bond pair leads to a HOH bond angle lower than the tetrahedral angle. The actual angle is 104.5°.

Thus, bond angle in water is less than that of ammonia.