# Question #3c1e2

Jun 22, 2016

You mean the oxidation number of $C o$ in $\text{cobaltous chloride}$, $C o C {l}_{2}$ is $+ I I$. Of course you may mean the oxidation state of inorganic $C$ in phosgene gas, $C {l}_{2} C \left(= O\right)$, which is $+ I V$.

#### Explanation:

The oxidation number is the charge left on the central atom when all of the bonding species are removed from it. Chlorine binds here as the ion chloride, $C {l}^{-}$. For a neutral molecule the sum of the oxidation numbers is zero:

$C {o}^{\text{Oxidation number}} - 2 \times 1 = 0$

The halogens normally have a $- I$ oxidation number.

Of course if you want the oxidation number of $C$ in $C {l}_{2} C = O$ this is $+ I V$.