Question

Choose the incorrect properties which shows the diagonal relationship of Li and Mg.

• A. Both carbonates decompose easily on heating
• B. Both $LiCl$ and $MgC{l}_2$ are soluble in ethanol
• C. Both form nitrides
• D. Both combine with excess oxygen to give superoxides.

Answer 1

The correct option is D Both combine with excess oxygen to give superoxides.

Due to similar size of Li and Mg they show similar properties.
Both Li and Mg react with $N_2$ to form respective nitrides
$3Mg+N_2\to M{g}_3{N}_2$
$6Li+N_2\to 2L{i}_{3}N$
Li and Mg form $L{i}_{2}O$ and MgO on reacting with oxygen. They don't combine with excess oxygen to give superoxides.
Due to polar nature of $LiCl$ and $MgC{l}_2$ both are soluble in ethanol.
Stability of carbonate increase down the group due to increase in electropositive character. So $L{i}_{2}C{O}_3$ and $MgC{O}_3$ are less stable so they are easily decomposed on heating.
Hence correct option is b.