The chemical formula for hydrogen peroxide is H2O2.
The formula shows that each molecule contains two hydrogen atoms and two oxygen atoms. Unlike water, whose formula is H2O, hydrogen peroxide contains an oxygen–oxygen single bond, making it the simplest member of the peroxide family. Its structure is often written H–O–O–H, although the molecule is bent and twisted rather than flat.
Pure hydrogen peroxide is a very pale blue liquid, but dilute household solutions usually look colorless. It is commonly sold in water at concentrations around 3% to 6% for consumer use and is used as an oxidizer, bleaching agent, and disinfectant. It decomposes into water and oxygen, especially when exposed to light, heat, or catalysts such as manganese dioxide.
The formula is easy to confuse with H2O because both substances contain hydrogen and oxygen. Their behavior is very different: water is relatively stable, while hydrogen peroxide is a reactive oxidizing compound. Concentrated hydrogen peroxide can decompose rapidly and dangerously, so consumer solutions should not be treated as harmless simply because they resemble water.