The oxidation number of the carbon atom in the carbonate ion (CO3²⁻) is +4.
To determine the oxidation number, we need to consider the overall charge of the ion and the typical oxidation states of the other atoms involved. In CO3²⁻, oxygen usually has an oxidation number of -2. Since there are three oxygen atoms, their total contribution to the charge is 3 x (-2) = -6.
Let’s denote the oxidation number of carbon as x. The sum of the oxidation numbers in the ion must equal the overall charge of the ion, which is -2. Therefore, we set up the equation:
x + (-6) = -2
Solving for x gives:
x = -2 + 6 = +4
This means the oxidation number of carbon in the carbonate ion is +4.