## Chemistry: The Central Science (13th Edition)

The ligands $(en)_{2}$ and ($C_{2}O_{4})$ that surround the central metal atom $Co$ are $2+1=3$, but since these are bidentate ligand, the coordination number is 6 because 2 $en$ are present and 1 $C_{2}O_{4}$ is present ($2\times2) + (2 \times1) = 6$ Let us suppose the oxidation number of $Co$ is X. To find the oxidation number, we sum the known oxidation numbers and equal it to the charge on the complex. Also, $(en)_{2}= 2 \times (0)$ The overall charge is +1 on the complex, thus: $X+ 2 \times (0) + (-2) = +1$ $X -2 = +1$ $X= +3$ The oxidation number of $Co$ is +3