K3[Cr(ox)3] Let, x be the oxidation state of Cr in K3[Cr(C2O4)3]. Since, the overall charge on the complex is 0 , the sum of oxidation states of all elements in it should be equal to 0 . Therefore, +3+x+3(−2)=0 (oxalate is bidentate ligand and having −2 charge) or, x=+3. Hence, chromium is in +3 oxidation state. Cr⟶3d54s1 (ground state electronic configuration) Cr3+⟶3d34s0 (Excited state)
CN=6 ∴ oxalate is weak field ligand ∴3 unpaired electron in d-orbital. The hybridisation of chromium in the complex is d2sp3.