1. Identify the complex ion

The compound is: $\mathrm{Na}[\mathrm{Co}(\mathrm{bpy})\mathrm{Cl}_4]$

So the complex ion is: $[\mathrm{Co}(\mathrm{bpy})\mathrm{Cl}_4]^-$

because $\mathrm{Na}^+$ is the counter ion.

2. Find oxidation state of cobalt

Let oxidation state of Co be $x$.

• $\mathrm{bpy}$ (2,2'-bipyridine) is a neutral ligand, so its charge = $0$
• Each $\mathrm{Cl}^-$ has charge $-1$, and there are 4 chlorides, so total charge from chloride ligands = $-4$
• Overall charge on the complex ion = $-1$

Therefore, $x + 0 - 4 = -1$ $x = +3$

So, the magnitude of oxidation state of cobalt is: $3$

3. Find coordination number of cobalt

• $\mathrm{bpy}$ is a bidentate ligand, so it contributes coordination number $2$
• 4 chloride ligands are monodentate, so they contribute $4$

Hence, coordination number of Co is: $2+4=6$

4. Find the required sum

$\text{Sum} = \text{magnitude of oxidation state} + \text{coordination number}$ $= 3 + 6 = 9$

Final Answer

$\boxed{9}$