Nitrate (${\mathrm{NO}}_3^{-}$)

The nitrate ion, ${\mathrm{NO}}_3^{-}$, is an anion with one nitrogen connected to three oxygen chemical atoms and net electric charge $-1$ in units of elementary charge. Its 24 valence electrons admit three equivalent octet resonance structures; see Lewis structure for their construction and chemical resonance for their interpretation. The N–O connections are covalent bonds within the ion. See 7.2 Covalent Bonding.

A historical nitrate-recognition reaction involving reduction by iron(II) and formation of a brown iron–nitrosyl species. Nitrite, reagent contamination and procedural conditions can interfere.