(i) Ionisation Enthalpy : The ionisation energies of alkaline earth elements are higher than those of alkali metals due to higher nuclear charge and smaller radii.
(ii) Basicity of oxides : Oxides of alkali metals are stronger bases as compared to those of alkaline earth metals present in the same period.
e.g., when Na2O is dissolved in water, NaOH formed is a stronger base than when MgO is dissolved in water to form Mg(OH)2.This is due to higher ionisation energies of alkaline earth metals.
(iii) Solubility of hydroxides : Alkali metal hydroxides are more soluble in water as compared to the hydroxides of alkaline earth metals present in the same period. This is due to higher lattice energy of the hydroxides of alkaline earth elements as compared to those of alkali metals.