Question

In which of the following molecules, does the presence of a lone pair affect the bond angle?

• A. $N{H}_3$
• B. $H_{2}O$
• C. $S{F}_4$
• D. All of the above

Answer 1

The correct option is D All of the above

In $N{H}_3$ and $H_{2}O$ there are 3 bond pairs, 1 lone pair and 2 bond pairs, 2 lone pairs repectively and so for both of them the geometry is tetrahedral with an expected bond angle of ${109.5}^o$. Due to the presence of lone pairs, the bond angle decreases. The shapes of $N{H}_3$ and $H_{2}O$ are pryamidal and bent respectively.





In $S{F}_4$ there are 4 bond pairs and one lone pair and so it is $s{p}^{3}d$ hybridized having a geometry of trigonal bipyramidal. The lone pair is placed in the equatorial position (according to Bent's rule) to reduce the repulsion between lp-bp, giving this molecule a see-saw shape and thus a lesser bond angle than expected.




Hence in all the molecules, the bond angles are affected by the presence of lone pairs.