Iron has the chemical formula Fe from its Latin name, ferrum. Its atomic number is 26, and its molar mass is 55.845 grams per mole. It has a metallic gray color and is attracted to magnets. Iron is the second most-abundant metal on Earth.
Iron is a reactive element and reacts with most acids. Chemical compounds of iron in oxidation state +2 are called ferrous compounds, and are reducing agents. Ferric compounds contain iron in oxidation state +3, and are oxidizing agents. Pure iron corrodes in damp air to form rust. However, carbon-containing alloys, such as stainless steel, do not rust in normal conditions.