Iron is the second most abundant metal on earth. The concentration of iron is greatest at the inner core, which is mostly the metal, and it makes up by mass 35% of the Earth as a whole. It forms approximately 5% of the outer crust. Iron has two common oxidation states ? and ?. Iron loses 2 electrons to give Fe2 or three electrons to give Fe3 as oxides FeO iron(II) oxide or Fe2O3 iron(III) oxide.
Iron(III) oxides are used in the production of magnetic storage media in computers. Iron(III) oxide as red ochre is a mineral pigment, an insoluble substance used in paint.