The correct order of bond angles in ${\mathrm{AsF}}_3\left(\mathrm{P}\right); {\mathrm{AsCl}}_3\left(\mathrm{Q}\right);{\mathrm{AsBr}}_3\left(\mathrm{R}\right)$ and ${\mathrm{PI}}_3\left(\mathrm{S}\right)$ is :

 Bond angle ${96.2}^{\circ }$.

Here, the ${\mathrm{AsBr}}_3$ has the greatest and the ${\mathrm{AsF}}_3$ has the shortest bond angles among the three due to variance in size and electronegativity.