Write a note on hydration enthalpy of group $2$ elements (Alkaline earth metals).

(N/A) The hydration enthalpies of alkaline earth metal ions decrease with an increase in ionic size down the group. The order is $Be^{2+} > Mg^{2+} > Ca^{2+} > Sr^{2+} > Ba^{2+}$.
The hydration enthalpies of alkaline earth metal ions are larger than those of alkali metal ions due to their smaller size and higher charge.
Consequently,compounds of alkaline earth metals are more extensively hydrated than those of alkali metals.
For example,$MgCl_{2}$ and $CaCl_{2}$ exist as $MgCl_{2} \cdot 6H_{2}O$ and $CaCl_{2} \cdot 6H_{2}O$,whereas $NaCl$ and $KCl$ do not form such hydrates.