Final Answer:
The resonance forms of the nitrite ion, NO2^-, show one structure with a nitrogen-oxygen double bond and another with a nitrogen-oxygen single bond and a double bond with a different oxygen atom.
Explanation:
The nitrite ion, NO2^-, demonstrates resonance by having a delocalized electron structure. In the first resonance form, nitrogen is double-bonded to one oxygen atom and single-bonded to the other oxygen atom, while in the second form, the double bond is shifted to the other oxygen atom. Both structures maintain a total of 18 valence electrons around the nitrogen atom, fulfilling the octet rule.
The non-zero formal charges appear on the oxygen atoms in each resonance structure: one oxygen atom carries a -1 charge, while the other oxygen atom holds a neutral charge. The resonance forms depict the electron delocalization within the molecule, showcasing the stability derived from the delocalized pi electron system. This phenomenon explains the equal contribution of both resonance structures in the actual structure of the nitrite ion.