Lassaigne's test is used for the detection of which the following elements?

Nitrogen, sulphur, white turbidry halogens and phosphorus present in an organic compound are detected by Lassaigne's test. The elements present in the compound are converted from covalent form to the ionic form by fusing the compound with sodium metal. Following reactions take place

$\mathrm{Na}+\mathrm{C}+\mathrm{N}\stackrel{\mathrm{\Delta }}{⟶}\mathrm{NaCN}$

$2\mathrm{Na}+\mathrm{S}\stackrel{\Delta }{⟶}{\mathrm{Na}}_2 \mathrm{S}$

$\mathrm{Na}+\mathrm{X}\stackrel{\mathrm{\Delta }}{⟶}\mathrm{NaX}$