# What is the oxidation number of carbon in the ion (Co3)2-?

Oct 22, 2015

The carbon is fully oxidized. Therefore, it is $C , I {V}^{+}$.

#### Explanation:

The sum of the formal oxidation numbers in an a complex or compound ion must sum to the charge of the ion. Here the charge is $- 2$. Oxygen typically has an oxidation number of $- I I$, and it does here. So $3 \times - 2 + {C}_{O N} = - 2$. And what therefore is ${C}_{O N}$?

What is the oxidation number of carbon in oxalate ion, ${C}_{2} {O}_{4}^{2 -}$?

The oxidation number of the carbon is +4.

#### Explanation:

Oxygen normally has an oxidation state of -2.

Oxygen = three ions each with a charge of -2 = 3 x -2 = -6
The overall charge of the polyatomic ion is -2

This means that the oxidation number of the carbon must be +4.

Total charge = +4 + -6 = -2

Here is a video which discusses this topic by discussing how to determine oxidation numbers of elements in the bicarbonate and dichromate ions.

Video from: Noel Pauller

Hope this helps!