Chemistry - Complete s-block Question with Solution | TestHub

Alkaline-earth metals form dispositive ions, instead of unipositive ions, because the hydration energy of dipositive ions compensates the higher value of second ionization energy.
Heat of hydration of an ion depends upon the charge/radius ratio. Compared to the heats of hydration of alkali metal ions of comparable size, the heats of hydration of alkaline-earth metal ions are approximately four times greater, e.g.,$\mathrm{\Delta }{\mathrm{H}}_{\mathrm{h}\mathrm{y}\mathrm{d}}\mathrm{N}{\mathrm{a}}^{+}$(size 102 pm)
$=-397$kJ/mol;$\mathrm{\Delta }{\mathrm{H}}_{\mathrm{h}\mathrm{y}\mathrm{d}}\mathrm{C}{\mathrm{a}}^{2+}$(size 100 pm)
$=-1650$kJ/mol.