Compare the alkali metals and alkaline earth metals with respect to (a) ionisation enthalpy, (b) basicity of oxides and (c ) solubility of hydroxides.

Explanation

(i) Ionisation enthalpy . The ionisation enthalpy of alkaline metals (group 2) is more as compared to alkali metals (group 1) present in the same period due to smaller size and more symmetrical cofiguaration. For example,

(ii) Basicity of oxides . Oxides of alkali metals are stronger bases as compared to those of alkaline earth metals present in the same period . This is quite evident form the fact that when `Na_(2)O` is dissolved in water, NaOH formed is a
`Na_(2)O+H_(2)Oto2NaOH,MgO + H_(2)Oto Mg(OH)_(2)`
This is on account of lesser ionisation enthalpy lf alkali metals as compared to alkaline earth metals. Therefore, NaOH can release `OH^(-)` ions in solution more readily than `Mg(OH)_(2)`.
(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 on account of higher lattice enthalpy of the hydroxides of alkaline earth family as compared to those of alkali metals.