A coordination complex cation is given by the formula [ M ( en )₂( C ₂ O ₄)]^+ , where M is a 3d transition metal. If the central metal ion M has a d^3 electronic configuration, identify the metal M .

Step-by-step solution

Let the oxidation state of the metal M be x . The ligand ethylenediamine ( en ) is neutral, and oxalate ( C ₂ O ₄²⁻ ) has a charge of -2 . For the complex [ M ( en )₂( C ₂ O ₄)]^+ , the sum of oxidation states is equal to the net charge: x + 2(0) + (-2) = +1 x = +3 The metal ion M ³⁺ has a d^3 electronic configuration. This means the neutral metal atom M must have 3 + 3 = 6 valence electrons ( 4s^1 3d^5 or 4s^2 3d^4 ). Looking at the 3d series: V (Group 5): 4s^2 3d^3 V ³⁺ is 3d^2 Cr (Group 6): 4s^1 3d^5 Cr ³⁺ is 3d