As K+ ion carries charge = +1, charge on 3K ions = +3.
Hence charge on complex ion = +3. As each oxalate ion C2O2-4 has charge = +2, charge on three C2O2-4 = -6. Therefore charge on Fe should be = +3 i.e., oxidation number of Fe in the given complex = +3. Coordination number of ligand = No. of ligand x Denticity
= 3 x 2 = 6 .
