What is the oxidation number of oxygen?

The oxidation number of oxygen can vary depending on the compound in which it is found. In general, oxygen has an oxidation number of -2 in most compounds. This is because oxygen is highly electronegative and tends to gain electrons in chemical reactions.

However, there are some exceptions to this general rule. In compounds like hydrogen peroxide (H2O2), the oxidation number of oxygen is -1. In compounds like O2, the oxidation number of oxygen is 0. In oxoanions such as the sulfate ion (SO4^2-), the oxidation number of oxygen can be -2, -1, 0, or +2 depending on the compound.

Overall, the oxidation number of oxygen in compounds can vary, but it is most commonly found as -2.