Chemistry - Complete s-block Question with Solution | TestHub

The reaction sequence is:

$M+N_2\to Nitride\stackrel{H_{2}O}{\to }N{H}_3$

For a metal M to react directly with N₂ to form a nitride, and then produce NH₃ upon hydrolysis, it must be capable of forming a stable nitride. Among the given options, only lithium (Li) and magnesium (Mg) react directly with atmospheric nitrogen to form nitrides (Li₃N and Mg₃N₂ respectively). Other alkali metals (like Cs) do not readily form nitrides under normal conditions.

The reactions are:

$6Li(s)+N_2(g)\to 2L{i}_{3}N(s)$

$3Mg(s)+N_2(g)\to M{g}_3{N}_2(s)$

Upon hydrolysis:

$L{i}_{3}N(s)+3H_{2}O(l)\to 3LiOH(aq)+N{H}_3(g)$

$M{g}_3{N}_2(s)+6H_{2}O(l)\to 3Mg(OH{)}_2(s)+2N{H}_3(g)$

Therefore, both Li and Mg can be metal M.

The final answer is $\boxed{D}$