Explain the reason for the fusion of an organic compound with metallic sodium for testing nitrogen,sulphur and halogens.

(N/A) Nitrogen,sulphur,and halogens are covalently bonded in organic compounds. For their detection,they have to be first converted to their ionic forms. This is achieved by fusing the organic compound with sodium metal,a process known as $Lassaigne's$ test. The chemical equations involved are:
$Na + C + N \longrightarrow NaCN$
$Na + S + C + N \longrightarrow NaSCN$
$2Na + S \longrightarrow Na_{2}S$
$Na + X \longrightarrow NaX$
$(X = Cl, Br, I)$
Here,$C$,$N$,$S$,and $X$ represent elements derived from the organic compound.