Peroxide ion (O₂²⁻)
- Charge
- −2
- Atoms
- O × 2
- Atoms in total
- 2
- Mass of the ion
- 31.998 g/mol
Peroxide is two oxygen atoms joined by a single bond, carrying a 2− charge. Each oxygen has an oxidation state of −1 instead of the usual −2, so the pair adds up to 2−. You meet the peroxide group in hydrogen peroxide, H₂O₂, used as an antiseptic and bleach, and in metal peroxides that bleach materials or release oxygen.
- Peroxide ends in -ide like oxide, O²⁻, but it has two oxygen atoms held together by an O–O bond.
- Do not confuse peroxide with superoxide, O₂⁻, which has the same two atoms but only a 1− charge.
- Lithium peroxide, Li₂O₂, absorbs carbon dioxide and gives off oxygen, which makes it useful for cleaning the air in spacecraft.