Assertion : The magnitude of the hydration enthalpies of alkaline earth metal ions () are much larger than those for the alkali metal ions.
Reason : The magnitude of hydration enthalpy depends upon the square of the charge on the ion.
(A). The magnitude of hydration enthalpy depends upon the square of the charge on the ion. Since, charge on the divalent ion (alkaline earth metal cation) is double than that on the monovalent ion (alkali metal cation), hence the hydration enthalpy of alkaline earth metal cations () should be nearly four times that of the alkali metal cations ().