Question

What is the oxidation number of carbon in CO2?

Answer 1

`4+`

Explanation:

Since oxygen is in group 6 on the periodic table, its valency is `2-` and hence so is its oxidation number.
But there are 2 oxygen atoms for each carbon atom so the total negative charge due the oxygen is `4-`
But since a molecule must have a net charge of zero in the free form, it implies that the oxidation number of the carbon atom must then be `+4`

Answer 2

Two oxygens and one carbon; carbon clearly has `IV^+` oxidation state.

Explanation:

What is the oxidation state of carbon in methane, ethane, and carbon monoxide?