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| Fe | |
|---|---|
| Name | Iron |
| Atomic number | 26 |
| Category | Transition metal |
| Appearance | Lustrous metallic, silvery-gray |
| Standard state | Solid (298 K) |
| Electron configuration | [Ar] 3d6 4s2 |
| Phase | Solid |
| Melting point | 1811 K |
| Boiling point | 3134 K |
| Density | 7.874 g cm−3 (293 K) |
Fe
Fe is the chemical element commonly known as iron, a transition metal central to metallurgy, geology, and biology. It is abundant in the Earth's crust and core and has shaped technologies from the Iron Age through modern steelmaking. Fe's unique electronic configuration underpins its magnetic, catalytic, and redox behavior exploited across industry and living systems.
The modern English name traces to Old English and Proto-Germanic roots alongside cognates in Latin and Greek classical literature. The chemical symbol is derived from the Latin name used by early alchemists and scholars associated with Roman Empire scholarship and medieval alchemical texts. Nomenclature formalization occurred during the development of modern chemistry in the 18th and 19th centuries with contributions from figures tied to Royal Society and continental academies.
Fe exhibits the characteristic properties of a transition metal: high tensile strength, ductility, and electrical and thermal conductivity. It crystallizes in body-centered cubic and face-centered cubic allotropes with phase transitions near temperatures studied in thermodynamics and materials science laboratories such as those at Max Planck Institute for Iron Research. Fe is ferromagnetic at ambient conditions with Curie behavior first quantified in studies influenced by Pierre Curie and subsequent work by Heike Kamerlingh Onnes. Its redox chemistry underpins catalysis in industrial processes pioneered by inventors connected to the Industrial Revolution and chemists associated with the Royal Institution.
Fe is the fourth most abundant element in the Earth by mass and predominates in the Earth's core as an iron-nickel alloy noted in geophysical models developed at institutions like Scripps Institution of Oceanography and Lamont–Doherty Earth Observatory. Economically important ores include hematite, magnetite, taconite, and goethite, mined in regions such as the Pilbara, Mesabi Range, Kurrama, and Carajás Mine. Commercial extraction uses blast furnaces and direct reduction technologies refined by corporations and engineers from companies like ArcelorMittal and innovations linked to the Bessemer process and metallurgists from the Metallurgical Society.
Fe has several stable isotopes with mass numbers 54, 56, 57, and 58; iron-56 is the most abundant and central to nucleosynthesis theory developed by astrophysicists at institutions such as CERN and observatories like Mount Wilson Observatory. Radioisotopes such as iron-59 and iron-55 are produced in reactors and cyclotrons at facilities including Oak Ridge National Laboratory and are used in tracer studies by researchers at medical centers like Mayo Clinic and Johns Hopkins Hospital.
Fe forms a wide range of coordination complexes and oxides central to inorganic chemistry curricula at universities such as University of Oxford and Massachusetts Institute of Technology. Common oxidation states are +2 and +3, giving rise to compounds like iron(II) sulfate and iron(III) oxide used in pigments and catalysis; mixed-valence compounds and organometallics were explored by chemists in the tradition of Alfred Werner and later groups at ETH Zurich. Iron–sulfur clusters are studied in theoretical and experimental labs affiliated with Max Planck Society for their roles in electron transfer and enzymatic catalysis.
Fe is essential in hemoproteins such as hemoglobin and myoglobin and in enzymes including cytochrome c and ribonucleotide reductase, with foundational biochemical research conducted at institutes like Rockefeller University and Pasteur Institute. Iron metabolism involves transport by transferrin and storage in ferritin studied by medical researchers at Harvard Medical School and Imperial College London. Iron deficiency causes anemia widely investigated by global health organizations including the World Health Organization, while iron overload disorders such as hemochromatosis and toxicity from particulate exposure have been subjects of clinical studies at centers like Cleveland Clinic.
Fe's dominant use is in steel production for infrastructure and transportation, industries shaped by firms like Tata Steel and historical projects including the Transcontinental Railroad. Iron and its alloys are critical in construction of bridges, ships, and automobiles designed by engineering firms and practiced in standards set by organizations such as American Society of Civil Engineers. Iron-based catalysts enable processes developed by chemical engineers at companies like BASF and in petrochemical complexes tied to large-scale refineries. In electronics, Fe-containing magnetic materials underpin devices from transformers to data storage researched at laboratories including IBM Research.
The transition from bronze to iron tools marks a major cultural shift exemplified by the Iron Age across regions like Mesopotamia, Anatolia, and Sub-Saharan Africa with archaeological work by teams from institutions such as the British Museum and Smithsonian Institution. Iconography and mythology involving iron appear in the corpus of Norse mythology, Hindu texts, and epic narratives preserved by scholars at universities like Cambridge and University of Tokyo. The strategic importance of iron shaped conflicts and industrial policy in eras including the Napoleonic Wars and both World War I and World War II, influencing economic and military historians at centers such as Yale University.