Group 2: thermal stability and solubility
Group 2 carbonates decompose on heating to the oxide and CO₂; nitrates to the oxide, NO₂ and O₂. Thermal stability increases down the group: small Mg²⁺ has high charge density and polarises (distorts) the large carbonate/nitrate ion, weakening its bonds, so MgCO₃ decomposes most easily. Down the group, cations get larger, polarise less, and higher temperatures are needed. Solubility: hydroxides get more soluble down the group; sulfates get less soluble. Solubility depends on the balance between lattice energy and hydration enthalpies: for sulfates, hydration enthalpy of the cation falls faster than lattice energy as the cation grows, so dissolving becomes less favourable.
≈ 40 min