The nitrate ion NO3- has three resonance structures. These structures are formed by the delocalization of the pi electrons in the molecule, which means that the electrons are spread out over the entire molecule rather than being localized between two specific atoms.The three resonance structures of NO3- are as follows:1. Structure 1: Nitrogen N is double-bonded to one oxygen O atom and single-bonded to the other two oxygen atoms. Each of the single-bonded oxygen atoms carries a negative charge.2. Structure 2: Nitrogen N is double-bonded to the second oxygen O atom and single-bonded to the other two oxygen atoms. The negative charge is now on the first oxygen atom.3. Structure 3: Nitrogen N is double-bonded to the third oxygen O atom and single-bonded to the other two oxygen atoms. The negative charge is now on the second oxygen atom.These resonance structures contribute to the stability of the nitrate ion in the following ways:1. Delocalization of electrons: The electrons are spread out over the entire molecule, which reduces the electron-electron repulsion and increases the overall stability of the molecule.2. Equivalent resonance structures: All three resonance structures are equivalent in terms of energy, which means that the actual structure of the nitrate ion is an average of these three structures. This equal distribution of electron density further stabilizes the molecule.3. Lowering of potential energy: The delocalization of electrons in the resonance structures lowers the potential energy of the molecule, making it more stable.In summary, the three resonance structures of the nitrate ion contribute to its stability by delocalizing the electrons, creating equivalent resonance structures, and lowering the potential energy of the molecule.