The HNH angle value is higher than HPH, HASH and HSbH angles. Why ?

Explanation

The central atom E (where, E is N, P, As, Sb, Bi) in all the given hydrides is sp hybridized. However, its electronegativity decreases and atom size increases on moving down the group. Therefore, there is a gradual decrease in the force of repulsion between electron pairs around the central atom . Thus , bond angle decreases as we move down the group.
`{:("Molecule",NH_(3),PH_(3), AsH_(3) , SbH_(3) , BiH_(3)),("Bond angle",106.8^(@), 93.6^(@), 91.8^(@), 91.3^(@),90^(@)):}`