Question

The alkali metal that can combine directly with nitrogen when heated in air is:

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

Answer 1

Answer: (B)

$Li$

Although the alkali metals possess a high chemical reactivity characteristic, lithium is the only element of the alkali metals to react with nitrogen gas at room temperature. The reaction between elemental lithium and nitrogen gas proceeds as follows producing the ionic (salt-like) lithium nitride (Li${}_3$N):

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

Hence, the correct option is $\text{B}$