... usually occur. Instead, the carbon atom, even though it retains a covalency of four, changed markedly in the degree of control it exerts over the covalently bound electrons. Thus, it may be that when the electron density about a carbon atom decreases, it has undergone oxidation, and conversely an increase in electron density can be interpreted as a reduction. Also the oxidation level or the oxidation number of a compound tells us whether an oxidation or reduction reaction has happened. There are a variety of methods of calculating oxidation numbers. In compounds such as methane, CH4, we know that hydrogen has an oxidation number of +1. Assuming that the algebraic sum of all the oxidation numbers must equal zero, the oxidation state of carbon in methane is therefore -4. When the oxidation number of an atom increases, that atom is said to be oxidised and when the oxidation number decreases, reduction ...

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