Bond angle in PH₄⁺ is higher than that in PH₃. Why ?

 P in PH₃ is sp³-hybridized. It has three bond pairs and one lone pair around P. Due to stronger lone pair-bond pair repulsions than bond pair-bond pair repulsions, the tetrahedral angle decrease from 109°. 28o to 93.6°. As a result, PH₃ is pyramidal. However, when it reacts with a proton, it forms PH₄⁺ ion which has four bond pair and no lone pair. Due to the absence of lone pair-bond pair repulsions and presence of four identical bond pair-bond pair interactions, PH₄⁺ assumes tetrahedral geometry with a bond angle of 109°. 28°. This explains why the bond angle in PH₄⁺ is higher than in PH₃.