Question

How would you calculate oxidation number?

Answer 1

There should be lots of examples on these boards where oxidation numbers of elements in different compounds have been (exhaustively!) assigned.

Explanation:

Oxidation number by definition is the charge left on the central atom, when each of the bonding pairs are broken, and the charge goes to the most electronegative atom.

I will take a simple example, `Cl-F`. Fluorine is the most electronegative element; if the `Cl-F` bond is broken we get the ions `Cl^+`, and `F^-`. So by the above definition oxidation numbers are (we use Roman numerals) `I^+`, and `I-`, for chlorine and fluorine respectively. The charges must sum up to the charge on the original species which was `0`.

I urge to look at the other questions on these boards where oxidation numbers are calculated step by step and assigned. Remember though, that oxidation numbers are a formalism; they don't really have much physical or chemical significance.