To determine the coordination number of chromium (Cr) in the complex K[Cr(H2O)2(C2O4)2], we need to identify the ligands and their denticity. Identify the central metal atom: The central metal atom is Chromium (Cr). Identify the ligands: H2O (aqua) C2O4 (oxalato, derived from oxalic acid, C2O42− ) Determine the denticity of each ligand: H2O (water): This is a monodentate ligand, meaning each water molecule forms one coordinate bond with the central metal atom. C2O42− (oxalate): This is a bidentate ligand, meaning each oxalate ion forms two coordinate bonds with the central metal atom, typically through its two oxygen atoms. Calculate the total number of coordinate bonds: There are two H2O ligands. Since each is monodentate, they contribute 2×1=2 coordinate bonds. There are two C2O42− ligands. Since each is bidentate, they contribute 2×2=4 coordinate bonds. Sum the coordinate bonds to find the coordination number: Coordination number =(. bonds from H2O)+(. bonds from C2O42−) Coordination number =2+4=6 Therefore, the coordination number of chromium in the given complex is 6 . The final answer is 6 .