Question

Although geometrics of ${NH}_3$ and $H_{2}O$ molecules are distorted tetrahedral, bond angle in water in less than that of ammonia. Explain.

Answer 1

In $H_{2}O$ there are two lone pairs of electrons whereas in $N{H}_3$ there are only one lone pair of electron.

In $H_{2}O$, lone pair-lone pair repulsion takes place whereas in $N{H}_3$ lone pair-bond pair repulsion takes place.

The lone pair-lone pair repulsion is more strong than lone pair-bond pair repulsion.

Thus, the bond angle in a water molecule is less than the ammonia molecule.

Bond angle $\alpha \frac{1}{No.oflP}$ (for same hybridisation compound)

$lP=$ lone pair