Question

What is this oxidation number of `CH_3OH` and `CH_2O`?

Answer 1

Given that oxidation number is an empirical concept; the oxidation number of `C` in methanol is `-II`; in formaldehyde it is `0`.

Explanation:

Oxidation number/oxidation state is an empirical construct, It is formally the charge left on the central metal atom when all the bonds are broken, with the charge devolving to the most electronegative atom.

On the Pauling scale, we can quote the electronegativities of `C,H, and O` as `2.55, 2.20, 3.44`. The means that the oxidation number of `C` in methane, `CH_4`, is `-IV`, and the oxidation number of `C` in carbon dioxide, `CO_2` is `+IV`.

Note that the SUM of the oxidation numbers equals the charge on the ion. Thus the oxidation number of `C` in `CO_3^(2-)` `=+IV (i.e. -2=C_"ON"+3xx(-2)`