Oxidation state

Oxidation state is like a point score for atoms. In chemistry, the atoms in a molecule can share the electrons in their outer shell. Oxidation state is like a score for each of these atoms, based on how many electrons it has in its outer shell. A higher score means that the atom has more electrons in its outer shell. The score can be a positive number (which means it has more electrons), or a negative number (which means it has fewer electrons). When atoms join together to make molecules, the total oxidation state of all the atoms must add up to zero.