Question

Is nitrate ion a ligand?

Answer 1

1. Ligand: An atom, molecule or ion which donates a pair of electrons to the central metal atom or ion to form a coordination compound, is called ligand.
2. Nitrate has ionic formula ${\mathrm{NO}}_3^{-}$ in which the oxygen atom is invariably coordinated with metal.

Hence, nitrate is a ligand.