Nitrogen gas is obtained by thermal decomposition of:

We need to identify which compound gives nitrogen gas ($$N_2$$) on thermal decomposition. Option A: $$NaNO_2$$ (Sodium nitrite) decomposes on heating but does not produce $$N_2$$ gas directly; it can decompose to give $$Na_2O$$, $$NO$$, and $$NO_2$$.

Option B: $$NaNO_3$$ (Sodium nitrate) decomposes on heating as:

$$2NaNO_3 \xrightarrow{\Delta} 2NaNO_2 + O_2$$

This gives oxygen gas, not nitrogen gas.

Option C: $$Ba(N_3)_2$$ (Barium azide) decomposes on heating as:

$$Ba(N_3)_2 \xrightarrow{\Delta} Ba + 3N_2$$

This gives pure nitrogen gas ($$N_2$$).

Option D: $$Ba(NO_3)_2$$ (Barium nitrate) decomposes on heating as:

$$2Ba(NO_3)_2 \xrightarrow{\Delta} 2BaO + 4NO_2 + O_2$$

This gives $$NO_2$$ and $$O_2$$, not $$N_2$$.

Azides ($$N_3^-$$) are compounds that contain three nitrogen atoms bonded together; on thermal decomposition, they readily release nitrogen gas ($$N_2$$). Barium azide is a well-known source of pure nitrogen gas upon heating. The correct answer is Option C: $$Ba(N_3)_2$$.