The correct order of the bond angles is

Options

A. `NH_3 gt H_2O gt PH_3 gt H_2S`
B. `NH_3 gt PH_3 gt H_2O gt H_2S`
C. `NH_3 gt H_2S gt PH_3 gt H_2O`
D. `PH_3 gt H_2S gt NH_3 gt H_2O`

Answer

A

Explanation

The bond angles depend upon electronegativity of the central atom and number of lone pair of electrons. Greater the electronegativity and more the number of lone pairs, smaller the angle. Since the clectronegativities of N (3.0) and O (3.5) are close, but `NH_3` has one and `H_2O` has two lone pairs of electrons, therefore bond angle in `NH_3` is larger `(107^@)` than in water `(104.5^@)`. Similarly, the electronegativities of P (2.1) and S (2.5) are close but `PH_3` has one while `H_2S` has two lone pairs of electrons, therefore, bond angle in `PH_3 (92.2^@)` is greater than `H_2S`.