Although geometries of NH3 and H2O molecules are distorted tetrahedral, the bond angle in water is less than that of ammonia. Discuss.
In NH3, there is only one lone pair on nitrogen atom to repel the bond pairs whereas in H2O there are two lone pairs on O-atom to repel the bond pairs as shown below:
Hence, the repulsion on bond pairs are greater in H2O than in NH3 and hence the bond angle is less.
Note More the no. of lone pairs on an atom, greater will be the repulsion and as a result, less will be the bond angle.
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