The oxidation number of Mg in Mg+2 is +2.
Oxidation number or state of an atom/ion is the number of electrons an atom/ion that the molecule has either gained or lost compared to the neutral atom.
- The oxidation number of an atom is defined as the charge that an atom appears to have on forming ionic bonds with other heteroatoms.
- Atoms in elemental form have an oxidation number of zero. For example, Mg, H2, Ar and Fe(s) are all examples of atoms in their elemental states.
- In the case of Mg2+ 2 electrons are lost and hence the oxidation number of Mg in Mg2+ is 2.