Iron (pronounced /ˈаɪ.ərn/) is a chemical element with the symbol Fe (Latin: ferrum) and atomic number 26. Iron is a group 8 and period 4 element. Iron and iron alloys (steels) are by far the most common metals and the most common ferromagnetic materials in everyday use. Fresh iron surfaces are lustrous and silvery-grey in colour, but oxidise in air to form a red or brown coating of ferrous oxide or rust. Pure single crystals of iron are soft (softer than aluminium), and the addition of minute amounts of impurities, such as carbon, significantly strengthens them. Alloying iron with appropriate small amounts (up to a few per cent) of other metals and carbon produces steel, which can be 1,000 times harder than pure iron.
Iron-56 is the heaviest stable isotope produced by the alpha process in stellar nucleosynthesis; heavier elements than iron and nickel require a supernova for their formation. Iron is the most abundant element in the core of red giants, and is the most abundant metal in iron meteorites and in the dense metal cores of planets such as Earth.
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