Core Reactions: Redox
Slide 18 of 42
Fractional Oxidation State
For example, let’s look at the charge and/or oxidation state of Fe in Fe3O4.
–Assuming oxidation state (or charge) of O is “2-” that of Fe comes out to 8/3rd.
Is that the charge on the Fe atom in the oxide?
–Not really (how can an atom have a fraction of a charge?!).
Is that the oxidation state of Fe in this compound?
–Yes. (It turns out to be the average oxidation state of Fe in the compound.)
Oxidation state therefore is not an intrinsic property of an atom; it is merely a book keeping system more than anything.
And as such, it is a great tool in balancing redox reactions--reactions involving reduction and oxidation.
(Check oxidation state of phosphorus in P4H2, sulfur in S3O62- and S4O62-.)
What about oxidation state of C in CH2O and CH3OH?
–While O and H have oxidation states of “2-” and “1+” respectively, carbon has oxidation state of “0” in CH2O and “2-” in CH3OH.