Oxidation Number of Cobalt (Co) in the Coordination Compound [Co(NH₃)₄(H₂O)₂Cl]Cl₂

1. Identify the overall charge of the complex ion
2. Assign known oxidation states to the ligands
   • $\text{NH3}$ (ammonia) is a neutral ligand, so its oxidation state is 0.
   • H2O (water) is also a neutral ligand, so its oxidation state is 0.
   • Cl^-1 (chloride) within the coordination sphere has an oxidation state -1.
   • Coordination sphere [Co(NH₃)₄(H₂O)₂Cl]⁺²
3. Set up the equation to find the oxidation state of Co:

Let the oxidation state of Co be x

x+4(0)+2(0)+(−1)= +2

=x + 4(0) + 2(0) + (-1) = +2.

$x+0+0+(-1)$$=+2$

=x-1=+2

=x=+2+1=+3

Therefore, the oxidation number of Co in [Co(NH3)4(H2O)2Cl]Cl2 is +3.