Question

Bond angle in $P{H}_4^{+}$ is higher than that in $P{H}_3$. Why?

Answer 1

Bond angle in $P{H}_4^{+}\text{and}P{H}_3$

In both $P{H}_3\text{and}P{H}_4^{+}$ ion, the phosphorus atom is $s{p}^3$ hybridised. However, in $P{H}_3$ the central atom has pyramidal structure due to the presence of Ione pair of electron on the phosphorus atom.

lp-bp Repulsion > bp-bp Repulsion

Because of the repulsion between lone pair and shared pair of $e^{-}$ which is more than that of shared pair and shared pair repulsion, the bond angle in $P{H}_3$ is nearly ${93.6}^{\circ }$.

In $P{H}_4^{+}$ ion, there is no electron lone pair on the phosphorus atom. It has a tetrahedral structure with bond angle of ${109}^{\circ }{28}^{\prime }$. Thus, the bond angle in $P{H}_4^{+}$ ion is higher than in $P{H}_3$.