KVPY2018ChemistryChemical Bonding and Molecular Structure
Among the following species, the H - X - H angle ( X = B ,   N or P ) follows the order.
Options
- APH 3 < NH 3 < NH 4 + < BF 3
- BNH 3 < PH 3 < NH 4 + < BF 3
- CBF 3 < PH 3 < NH 4 + < NH 3
- DBF 3 < NH 4 + < NH 3 < PH 3
Correct answer
A. PH 3 < NH 3 < NH 4 + < BF 3
Step-by-step solution
As the electronegativity of the central atom increases the bond angle also increases. So, NH 3 will have high bond angle than PH 3 . The bond angle of NH 4 + is highest because of its symmetrical geometry, also bond pair and lone pair on N of NH 3 suffer repulsion, which decreases its bond angle in comparison to NH 4 + . Thus, the correct order of bond angle is PH 3 < NH 3 < NH 4 + But in the given question none of the option is correct because there is no H - X - H bond angle in BF 3