Solubility of sulphates goes on decreasing down the group because lattice energy dominates over hydration energy. Lithium has smallest atomic size and highest ionization energy, highest polarizing power that is why it shows uncommon properties to the rest of alkali metals.
(i) Both Lithium and Magnesium react with N2 to form nitrides.
(ii) Li and Mg react with O2 to form monoxides.
