What is the oxidation number of iron in Fe3O7 ?

1 Answer
Nov 5, 2015

In #Fe_3O_7# Iron has an Oxidation Number of #4 2/3#


Oxidation numbers are calculated through a set of rules. Oxygen is an atom that has only 3 possible Oxidation numbers:

  1. If Oxygen is bonded to itself (Mainly in #O_2# ) then it has an Oxidation number of 0. This is true of any atom that bonds to itself with few exceptions.
  2. If Oxygen is in the form of Peroxide #O_2^-2# then it will have an oxidation number of -1.
  3. In all other cases Oxygen will have an Oxidation Number of -2.

Since your molecule has Iron bonded to Oxygen and that Oxygen is not in the form of Peroxide. It follows that each Oxygen has an Oxidation number of -2.

That gives all of the Oxygen a cumulative Oxidation Number of -14. All molecules must have a Net Oxidation Number equal to their charge (in this case 0). Meaning that the 3 Irons must add up to +14 cumulatively.

Simple division then leads you to determine that the +14 distributed across 3 Iron atoms will have an Oxidation number of #14/3# or #4 2/3#.