What is the formula for the sulfite ion?

The sulfite ion is represented by the formula SO3 2-. This designation indicates that the ion contains one sulfur atom (S) bonded to three oxygen atoms (O), and it carries an overall charge of -2.

Understanding the structure of sulfite is essential: sulfur typically exhibits a +4 oxidation state in sulfite, and each of the three oxygen atoms is bonded to the sulfur atom. The charge of -2 arises because sulfite has two fewer electrons than protons, which also corresponds to the loss of bonding that would balance to neutrality with additional oxygens or hydrogen ions.

In contrast, the other options represent different ions. The sulfate ion, which is denoted as SO4 2-, contains a sulfur atom bonded to four oxygen atoms and also carries a -2 charge, but it is not the same as sulfite. The SO2 2- ion corresponds to the thiosulfate anion, which has a sulfur-sulfur bond and is not relevant here. Finally, the notation SO3 +2 suggests a species with a positive charge, which does not correspond to the sulfite ion's true identity or charge characteristics.

Recognizing these differences helps clarify why the sulfite ion is correctly identified by its formula