which has lowest bond angle?

AsCl3, SbCl3, PCl3 , NCl3 ( ANSWER=SbCl3) why???

In the given series, central atoms belong to group 15. As we move down the group size of central atom increases along with decrease in electronegativity which results in the greater repulsion between the lone pair to bond pair, making bond pair and bond pair to contract more resulting in decreased bond angles.

As Sb is largest in size with lowest electronegativity, the greater repulsion between the lone pair to bond pair occurs, making bond pair and bond pair to contract more resulting in lowest bond angles.