Hint: The elements in group one of the periodic tables (except for hydrogen-see below) are known as alkali metals since, when they react with water, they form alkaline solutions. Group two of the periodic table contains beryllium, magnesium, calcium, strontium, barium and radium elements. The elements in this group, which all appear brilliant and silvery-white, are known as alkaline earth metals.
Alkaline earth metal, any of the six chemical elements forming Group 2 ($IIa$) of the table. The components are beryllium$\left( Be \right)$, magnesium$\left( Mg \right)$, calcium$\left( Ca \right)$, strontium$\left( Sr \right)$, barium $\left( Ba \right)$and radium $\left( Ra \right)$.Alkali metal, any of the six chemical elements that compose Group 1 $\left( Ia \right)$of the periodic table—namely, lithium $\left( Li \right)$,sodium $\left( Na \right)$,potassium$\left( K \right)$, rubidium $\left( Rb \right)$, cesium $\left( Cs \right)$, and francium $\left( Fr \right)$.
(i)Ionization enthalpy: Alkaline earths have a higher ionization enthalpy value than alkali metals. This can be because the atomic size of alkaline earths is smaller than that of alkali metals.
(ii) Basicity of oxides: On dissolution in water, the oxides of alkali metals and alkaline-earth metal metals form basic hydroxides. The basicity of metallic element oxides is more than that of metallic element metal oxides. And as know it’s all because of the lower ionization enthalpy of alkali metals than that of corresponding alkaline earths. Because of which, the $M-OH$ bond in metal hydroxides can more easily ionize.
(iii) Solubility of hydroxides: Alkaline earths have larger lattice energies than alkali metals because of small size and a high charge. Hence, metallic element metal hydroxides have lower solubility than alkali metals.
Note: The energy ionisation is the amount of energy needed by an isolated gas atom to lose the electron in its ground state.
Basic oxides are oxides which have basic properties as opposed to acidic oxides and which either react with water to form a base; or react with acid to form a salt and water called neutralisation reactions.
Solubility of hydroxides is when hydroxides are completely ionized.