Statement 1 : To obtain effective $\mathrm{p\pi }-\mathrm{d\pi }$ overlap, the size of the d-orbital must be similar to the size of the p-orbital. So for chlorine $\mathrm{p\pi }-\mathrm{d\pi }$ bonding is strongest in their oxoanions.

Statement 2 : On moving a period from left to right in the periodic table, the nuclear charge is increased and more s and p-electrons are added. Since these s- and p-electrons shield the nuclear charge incompletely, the size of the atom and that of the d-orbitals decreases. This leads to progressively stronger $\mathrm{p\pi }-\mathrm{d\pi }$ bonding.