of central atom increases which weakens the

$\mathrm{M}-\mathrm{H}$ bond. Since, the size increases from $\mathrm{S}$ to $\mathrm{Te}$

thus acidic strength follows the order.

$H_{2} S < H_{2} S e < H_{2} T e$

Acidic nature $\propto \frac{1}{\text { Bond disspciation enthalpy }}$

$S$ to $Te$ size increases, bond dissociation enthalpy

decreases and acidic nature increases.