Iron

Iron is a lustrous, magnetic transition metal whose mastery — from the Iron Age to the blast furnace — reshaped human civilization. It is strong, workable, and abundant, and alloying it with carbon creates the vast family of steels that build the modern world. Exposed to moist air it rusts, forming flaky hydrated iron(III) oxide.

Iron lives at the center of biology too: hemoglobin carries oxygen in blood using an iron atom in each heme group, and iron deficiency is the world's most common nutritional disorder. Its two everyday oxidation states, +2 and +3, color countless minerals and pigments.

Key facts

Occurrence

Iron is the fourth most abundant element in Earth's crust and the most abundant element in the planet overall, forming much of the core. It is mined as hematite and magnetite ores. Free metallic iron is rare on the surface but falls from the sky in iron-nickel meteorites.

Applications

• Structural steel for buildings, bridges, and vehicles is iron's dominant use

• Cast iron serves in engine blocks, pipes, and cookware

• Permanent magnets in motors and generators use iron alloys

• Hemoglobin in red blood cells carries oxygen using iron at its core

• The Haber process uses iron catalysts to make ammonia for fertilizers

Common compounds

• iron(III) oxide
• iron(II) sulfate
• iron(III) chloride
• iron pyrite

Data source: IUPAC standard atomic weights 2021

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