Final answer:
The sulfite ion (SO₃⁻⁻) has three resonance structures, each featuring sulfur bonded to three oxygens with two single bonds and one double bond in different positions, while the true structure is a hybrid reflecting electron delocalization.
Step-by-step explanation:
The molecule SO₃⁻⁻ (sulfite ion) can be represented by various resonance forms which describe the distribution of electrons within the ion. Resonance forms show the delocalization of electrons by depicting different possible arrangements of double and single bonds without changing the position of atoms. In the resonance structures of the sulfite ion, sulfur is bonded to three oxygen atoms. There are two single bonds and one double bond to sulfur in each structure. However, the double bond can be between sulfur and any one of the three oxygen atoms, leading to three possible resonance structures. In each structure, the unbound oxygen atoms—those not double-bonded to sulfur—will carry a single negative charge to complete the overall -2 charge of the ion.
In each resonance structure, sulfur has an expanded octet and is able to accommodate more than eight electrons around it. These are distributed as four pairs of bonding electrons (two in each single bond and four in the double bond) and one lone pair not involved in bonding. The true structure is a hybrid of all these resonance forms, indicating electron delocalization across the sulfur-oxygen bonds.