Question

Calculate the oxidation number of the central metal atom (underlined) in the following complex specie:

[Fe(C₂O₄)₃]³⁻

Answer 1

The complex ion is: [Fe(C₂O₄)₃]³⁻

C₂O₄²⁻ (oxalate ion) is a bidentate ligand with a charge of –2 each.

Overall charge on the complex = –3.

Let the oxidation number of Fe be x.

x + 3(−2) = −3

x − 6 = −3

 x = −3 + 6

x = +3

Thus, the oxidation number of Fe is +3.