How would you calculate oxidation number?

1 Answer
Oct 31, 2015

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


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.