Question

The metal that forms a nitride by reacting directly with atmospheric $N_2$ is:

• A. $Li$
• B. $Rb$
• C. $K$
• D. $Cs$

Answer 1

The correct option is A $Li$

$Li$ reacts with $N_2$ to form $L{i}_{3}N$ because of the small size of $Li$.

$6Li+N_2\to 3L{i}_{2}N$

The lattice energy released from the formation of $L{i}_{3}N$ is high enough to make the overall reaction exothermic. For all the other alkali metals, the lattice energy is not high enough.