Which of the following are ionic compounds?

(P) ${\mathrm{NH}}_2{\mathrm{NO}}_2$    (Q) ${\mathrm{NH}}_4{\mathrm{NO}}_3$

The ammonium cation ${\left({\mathrm{NH}}_4\right)}^{+}$ and the nitrate anion ${\left({\mathrm{NO}}_3\right)}^{-}$ combine to form the ionic salt known as ammonium nitrate. This substance has the chemical formula ${\mathrm{NH}}_4{\mathrm{NO}}_3$