In [Fe(C2O4)3]3−, three bidentate C2O42− ligands, that is, total six donor atoms are attached to ferric ion (Fe3+). Therefore, the coordination number of Fe3+ ion in the complex is six. When coordination number (C.N.) of the metal ion in the complex is to be determined, always check the type of the ligands. In case of monodentate ligands, C.N.=1× (No. of monodentate ligands bound to the metal) and in case of bidentate ligands, C.N. =2× (No. of bidentate ligands bound to the metal).