Aqueous ammonium nitrite, $\text{NH}_4\text{NO}_2$, breaks down on heating. $\text{NH}_4\text{NO}_2(\text{aq}) \rightarrow \text{N}_2(\text{g}) + 2\text{H}_2\text{O}(\ell)$ For this salt, the anion is ......1...... . During the reaction, the nitrogen atoms in the ......2...... ion are oxidised. Which formulae correctly fill gaps 1 and 2?