What is the oxidation number of carbon in CO2?
Since oxygen is in group 6 on the periodic table, its valency is
But there are 2 oxygen atoms for each carbon atom so the total negative charge due the oxygen is
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
Two oxygens and one carbon; carbon clearly has
What is the oxidation state of carbon in methane, ethane, and carbon monoxide?