In peroxides, the oxidation number of oxygen is:

Explanation

In peroxides, the oxidation number of oxygen is -1. This is due to the peroxide ion (O2²⁻), where two oxygen atoms are bonded together, sharing a -2 charge, which results in each oxygen having an oxidation state of -1. For example, in hydrogen peroxide (H2O2), the oxidation number of each oxygen atom is -1, balancing the +1 oxidation state of the hydrogen atoms.Options B (2) and D (1) are incorrect because oxygen typically does not have a positive oxidation state in compounds due to its high electronegativity. Option C (-2) is incorrect in the context of peroxides, as this is the oxidation number for oxygen in most other compounds but not in peroxides.