Järn

Järn, with the chemical symbol Fe and atomic number 26, is a transition metal that is both abundant in the Earth’s crust and central to modern technology. It has a density of about 7.87 g/cm3, a melting point of 1538°C, and a boiling point of 2862°C. In its elemental form at room temperature it is ferromagnetic, a property that diminishes at higher temperatures (below its Curie point of about 770°C). Iron forms several oxides, notably FeO, Fe2O3 (hematite), and Fe3O4 (magnetite), and it commonly exhibits oxidation states of +2 and +3 in compounds.

Iron is primarily produced by reducing iron ore in a blast furnace using coke, which yields pig iron that is subsequently refined into steel or cast iron. The large-scale production and use of iron and its alloys—especially steel and stainless steel—underpin much of modern industry, construction, transportation, and machinery. Steel quality is tuned by adjusting carbon content and adding alloying elements such as chromium, nickel, and vanadium.

Biologically, iron is essential for most organisms. It is a key component of hemoglobin and myoglobin, enabling oxygen transport and storage. Iron homeostasis is tightly regulated; both iron deficiency and iron overload can cause serious health problems. In the environment, iron readily corrodes in moist air to form hydrated iron(III) oxides, commonly known as rust.

Historically, iron metallurgy propelled the transition from the Bronze Age to the Iron Age and later enabled advanced steelmaking techniques, including the Bessemer process, which facilitated mass production of steel. In Swedish, järn denotes this element, while its chemical symbol Fe derives from ferrum.