# How would you calculate oxidation number?

Oct 31, 2015

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, $C l - F$. Fluorine is the most electronegative element; if the $C l - F$ bond is broken we get the ions $C {l}^{+}$, 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.