What is the formula for the peroxide ion?

The formula for the peroxide ion is represented as O2(2-). This indicates that the ion consists of two oxygen atoms bonded together (O2) and carries a charge of negative two. The peroxide ion is characterized by the presence of a peroxo bond, which is a single bond between the two oxygen atoms with an overall negative charge due to the addition of electrons.

In the context of other options, O2(-) represents a superoxide ion, which has only one negative charge and is not the same as peroxide. O(-) indicates a single oxygen atom with a negative charge, which does not reflect the molecular structure of the peroxide ion. Lastly, O3(2-) suggests a triatomic ion that does not correspond to the known structure or charge of the peroxide ion. Therefore, the correct choice clearly aligns with the recognized structure and charge of the peroxide ion.