The valence of nitrate is-1, where n is the highest valence +5, N atoms are bonded by sp2 hybrid orbital, there are three σ bonds in the ion, and the ion is a plane triangle. Nitrate ion is oxidizing, which can oxidize ferrous ion into iron ion in acidic solution and reduce itself to nitric oxide. Nitric oxide can combine with many metal salts to form unstable nitroso compounds.

Nitrate ion test

Nitrate ion is oxidizing, which can oxidize ferrous ion into iron ion in acidic solution and reduce itself to nitric oxide. Nitric oxide can combine with many metal salts to form unstable nitroso compounds. It reacts with ferrous sulfate to produce dark brown ferrous nitrossulfate. This reaction is often used to test nitrate ions in the laboratory, which is called Brownian ring test. This simple nitroso compound only exists in the solution, and when heated, nitric oxide completely escapes from the solution.

Refer to the above content: Baidu Encyclopedia-Nitrate