In peroxides, oxygen has oxidation number

In peroxides, oxygen has oxidation number

• A. -1
• B. -2
• C. 0
• D. +2

Answer: (A)

Oxygen in peroxides has an oxidation state of -1. This comes from the presence of an O–O bond. Take hydrogen peroxide, H2O2: each hydrogen is almost always +1, giving a total of +2 from hydrogen. The molecule is neutral, so the two oxygens together must contribute -2. Since the two oxygens are equivalent, they share that -2 equally, giving -1 on each oxygen. The same idea applies to the peroxide ion O2^2−, where the overall -2 charge is distributed between the two oxygens, again resulting in -1 per oxygen. This is different from a normal oxide, where oxygen is typically -2 because there isn’t an O–O bond to share that extra negative charge.

Oxygen in peroxides has an oxidation state of -1. This comes from the presence of an O–O bond. Take hydrogen peroxide, H2O2: each hydrogen is almost always +1, giving a total of +2 from hydrogen. The molecule is neutral, so the two oxygens together must contribute -2. Since the two oxygens are equivalent, they share that -2 equally, giving -1 on each oxygen. The same idea applies to the peroxide ion O2^2−, where the overall -2 charge is distributed between the two oxygens, again resulting in -1 per oxygen. This is different from a normal oxide, where oxygen is typically -2 because there isn’t an O–O bond to share that extra negative charge.