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Name: Bryan B.
Status: student
Age: 17
Location: N/A
Country: N/A
Date: 2001 - 2002

I was told by my high school chemistry teacher that the oxidation number of peroxide is misleading because it is not really -1. He said that -1 is not its charge, but a fictitious oxidation number. I was wondering what the real oxidation number was, and why we assign it a fictitious number of -1.

The term "fictitious" as used here does not mean "fake", rather it is a number assigned to a compound that denotes how many electrons a compound will "donate" or "accept" in an oxidation/reduction chemical reaction. A given compound may have more than one oxidation number depending upon what it is reacting with. Some simple examples are Cl2 ----> 2Cl(-) where the oxidation number is -1 per atom or -2 per molecule and Na -----> Na(+) is +1.

Electron donors are assigned positive numbers and electron acceptors are assigned negative numbers. Maybe a better term would have been "conventional" rather than "fictitious".

Vince Calder

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