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Question:

Both lithium and magnesium display several similar properties due to the diagonal relationships. However, the one which is incorrect is:

Both form basic carbonates.

Nitrates of both Li and Mg yield NO2 and O2 on heating.

Both form soluble bicarbonates.

Both form nitrides.

Solution:

Both Li and Mg combine directly with N2 to give nitrides Li3N2 and Mg3N2. Bicarbonates of Li and Mg are more soluble in water than carbonates whereas carbonates of alkali metals are more soluble. Hydroxides and nitrates of both Li and Mg decompose on heating to give oxide. LiNO3 Δ → Li2O + NO2 + O2 Mg(NO3)2 Δ → MgO + NO2 + O2 Magnesium forms basic carbonates (MgCO3.Mg(OH)2.xH2O) while lithium forms normal carbonates; it does not form basic carbonates.