Which statement is correct?
A.Sodium nitride has the formula $Na{N_3}$
B.K reacts with ${N_2}$ to give ${K_3}N$
C.Lithium nitride forms when Li reacts with ${N_2}$
D.Solid lithium nitride is a conductor

Hint: The molecular or chemical formula of Sodium Nitride is $N{a_3}N$ . Lithium is the only element of the alkali metals that reacts with nitrogen gas at room temperature. Lithium (Li) metal reacts with ${N_2}$ to form lithium nitride $(L{i_3}N)$

Complete step by step answer:
In option (A), it is given that Sodium nitride has the formula $Na{N_3}$ .
But sodium nitride is an inorganic compound which is a highly unstable alkali metal nitride.
Sodium is an element present in group 1 of the periodic table. As such, it will form an electron by losing a single electron to form a 1+ ion: $N{a^ + }$
Nitrogen is an element present in group 5 of the periodic table. When it forms the nitride ion, it gains three electrons to form a 3- ion: ${N^{3 - }}$ .
In ionic compounds, the charges of constituent ions must balance. This can be achieved by having three sodium ions per nitride ion. Therefore, the formula of sodium nitride is $N{a_3}N$ .
So, this option is incorrect.
In option (B), it is given that K reacts with ${N_2}$ to give ${K_3}N$ .
K does not react with ${N_2}$ to give ${K_3}N$ . But lithium is the only element of the alkali metals that reacts with nitrogen gas at room temperature. So, this option is also incorrect.
In option (C), it is given that Lithium nitride forms when Li reacts with ${N_2}$
Lithium (Li) metal easily reacts with ${N_2}$ to form lithium nitride $(L{i_3}N)$ at a relatively low temperature. Metallic Li possesses high reactivity to dissociate ${N_2}$ .
 $6Li(s) + {N_2}(g) \to 2L{i_3}N(s)$
So, only this option is correct.
In option (D), it is given that Solid lithium nitride is a conductor
But solid lithium nitride does not act as conductor in solid state but acts as insulator is solid state. So, this option is also incorrect.

Therefore, the correct answer is option (C).

Note: Lithium nitride $(L{i_3}N)$ is a thermodynamically stable material and difficult to be used as nitrogen sources. Molar mass of lithium nitride $(L{i_3}N)$ is 34.83 g/mol.