Group 2

Group 2 reactions and trends

Down group 2, atomic radius increases, first ionisation energy decreases, so reactivity increases. The metals react with water: Mg slowly (fast with steam to MgO + H₂), Ca–Ba readily to give hydroxide + H₂, e.g. $\mathrm{Ca+2H_2O\rightarrow Ca(OH)_2+H_2}$. Hydroxides become more soluble down the group (Mg(OH)₂ sparingly, Ba(OH)₂ soluble), so solutions become more alkaline. Sulfates become less soluble (BaSO₄ insoluble: used to test for sulfate and in barium meals). Uses: Ca(OH)₂ and CaCO₃ neutralise acid soils; Mg(OH)₂ in antacids.