Chapter 24 - Sections 24.1-24.6 - Exercises - Problems by Topic - Page 1125: 22c

Oxidation state= +2 Coordination number= 6

Let the oxidation state of the metal ion be $X$. We know that the charge on the oxalate ion is -2. Then, we have $X+3(-2)=-4$ $\implies X=+2$ As oxalate ion is a bidentate ligand, the number of ligand donor atoms to which the metal directly bonded is 2(3)=6. Therefore, coordination number= 6.