Which of the following has minimum bond angle?

Options

A. `SO_3`
B. `NOCl`
C. `NH_4^(+)`
D. `H_2Se`

Answer

D

Explanation

In `SO_3`, the SN of central S is `3+0=3`. Therefore, it is trigonal planar with bond angle exactly `120^@`. In `NOCl`, the central N has SN equal to `2+1=3`. Therefore, it is angular with bond angle slightly less than `120^@` due lone pair versus bond pair repulsion. In `NH_4^(+)`, the central N has SN equal to `4+0=4`. Therefore, it is tetrahedral with bond angle exactly `109.5^@`. The SN of Se in `H_2Se` is `2+2=4`. Therefore, it is angular with bond angle less than `109.5^@` due to lone pair versus lone pair repulsion.
Hence, we conclude that `H_2Se` has the minimum bond angle. In fact, its actual bond angle is `91^@`.