The ratio of ${\mathrm{p}}_{\pi }-{\mathrm{d}}_{\pi }$ bonds is ${\mathrm{SO}}_2$ and ${\mathrm{SO}}_3$ molecules

The structure of ${\mathrm{SO}}_2$ and ${\mathrm{SO}}_3$ molecule can be drawn as:

The number ${\mathrm{p}}_{\mathrm{\pi }}-{\mathrm{d}}_{\mathrm{\pi }}$ bond in ${\mathrm{SO}}_2$ is only one whereas in ${\mathrm{SO}}_3$ it is two.