Question

What is the oxidation number of Cobalt $\left(\mathrm{Co}\right)$ in $\mathrm{K}\left[\mathrm{Co}\right({\mathrm{C}}_2{\mathrm{O}}_4{)}_2.{\mathrm{NH}}_3]$ compound?

Answer 1

Oxidation number:

• It represents the number of electrons lost or gained by the atoms of an element in a compound.
• It is usually written with the sign $(+)$ and $(-)$ first and then the magnitude.

Determine the oxidation number of cobalt metal:

• The given coordination complex is: $\mathrm{K}\left[\mathrm{Co}\right({\mathrm{C}}_2{\mathrm{O}}_4{)}_2.{\mathrm{NH}}_3]$
• In this compound,$\mathrm{Co}$ is the cobalt metal, ${\mathrm{C}}_2{\mathrm{O}}_4$ named oxalate ion is having an oxidation state of $(-2)$ and ${\mathrm{NH}}_3$ named ammonia is a neutral ligand.
• Let the oxidation of $\mathrm{Co}$ be $\mathrm{x}$.

$$\begin{gathered} \mathrm{x}+2\times (-2)+0=-1 \\ \mathrm{x}-4=-1 \\ \mathrm{x}=-1+4 \\ \mathrm{x}=+3 \end{gathered}$$

Hence, the oxidation number of Cobalt $\mathbf{\left(}\mathbf{Co}\mathbf{\right)}$ in $\mathbf{K}\mathbf{\left[}\mathbf{Co}\mathbf{\right(}{\mathbf{C}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{4}}{\mathbf{)}}_{\mathbf{2}}\mathbf{.}{\mathbf{NH}}_{\mathbf{3}}\mathbf{]}$ compound is $\mathbf{+}\mathbf{3}$.