Why is bond angle in `PH_(4)^(+)` ion higher than in `PH_(3)` ?

Explanation

In both `PH_(3) " and " PH_(4)^(+)` ion, the phosphorus atoms is `sp^(3)` hybridised. However , in `PH_(3)` the central atom has a pyramidal structure due to the presence of lone electron pair on the phosphorus atom.

Because of lone pair : shared pair repulsion which is more than that of shared pair : shared pair repulsion, the bond angle in `PH_(3)` is nearly `93.6^(@)`. In `PH_(4)^(+)` ion, there is no lone electron pair on the phosphorus atom. It has a tetrahedral structure with bond angle of `109^(@)-28'`. Thus, the bond angle in `PH_(4)^(+)` ion is higher than in `PH_(3)`.