Question

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

• A. Both form soluble bicarbonates.
• B. Both form nitrides.
• C. Nitrates of both $Li$ and $Mg$ yield $N{O}_2$ and $O_2$ on heating.
• D. Both form basic carbonates.

Answer 1

Answer: (D)

Both form basic carbonates.

Both $Li$ and $Mg$ combine directly with $N_2$ to give nitrides $L{i}_3{N}_2$ and $M{g}_3{N}_2$.

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.

$LiN{O}_3\stackrel{\Delta }{\to }L{i}_{2}O+N{O}_2+O_2$

$Mg(N{O}_3{)}_2\stackrel{\Delta }{\to }MgO+N{O}_2+O_2$

Magnesium forms basic carbonates $(MgC{O}_3.Mg(OH{)}_2.x{H}_{2}O)$ while lithium forms normal carbonates, it does not form basic carbonates.