Compare the alkali metals and alkaline earth metals with respect to (i) ionisation enthalpy (ii) basicity of oxides and (iii) solubility of hydroxides.

Alkali metals

Alkaline earth metals

(i) Ionisation enthalpy: These have the lowest ionisation
enthalpies in respective periods. This is because of their large atomic sizes. Also, they lose their only valence electron easily as they attain stable noble gas configuration after losing it.

(i) Ionisation enthalpy: Alkaline earth metals have smaller
atomic size and higher effective nuclear charge as compared to alkali metals. This causes their first ionisation
enthalpies to be higher than that of alkali metals. However, their second ionisation enthalpy is less than the corresponding alkali metals. This is because alkali metals, after losing one electron acquires noble gas
configuration, which is very stable

(ii) Basicity of oxides: The oxides of alkali metals are
very basic in nature. This happens due to the highly
electropositive nature of alkali metals, which makes these
oxides highly ionic. Hence, they readily dissociate in water to give hydroxide ions.

(ii) Basicity of oxides: The oxides of alkaline earth metals are quite basic but not as basic as those of alkali metals. This is because alkaline earth metals are less electropositive than alkali metals.

(iii) The solubility of hydroxides: The hydroxides of alkali metals are more soluble than those of alkaline earth metals.

(iii) The solubility of hydroxides: The hydroxides of alkaline earth metals are less soluble than those of alkali metals. This is due to the high lattice energies of alkaline earth metals. Their higher charge densities (as compared to
alkali metals) account for higher lattice energies.