Most of the iron on our planet is housed in the Earth's hot, molten core. This element is found widely in rocks around the world, and nearly 2.5 billion tons are purified each year. Iron-rich minerals include pyrite. Others, including hematite, are used to extract pure iron by smelting. Iron-rich meteorites, are one of the few sources of pure natural iron. The human body uses iron to produce hemoglobin, a substance in the blood that transports oxygen around our body. Thus, iron-containing foods include meats and green vegetables, such as spinach. When pure iron comes into contact with air and water, it develops a reddish-brown, flaky coating called rust, which weakens the metal. To make the iron stronger and rust-free, small amounts of carbon and other metals, such as nickel and titanium, are added. In this way, an alloy called steel is formed, which is widely used in all kinds of manufacturing resistant materials applications. Also, adding chromium to steel creates a stronger alloy called stainless steel.

Iron accounts for at least 90% of the production of all metals. Without it we would not have power lines or oil refineries. Iron is a key component in the manufacture of all types of machinery: automobiles, trains, airplanes, ships, refrigerators, dishwashers and computers. As a chemical it is also used in insecticides, water purification, wastewater treatment and ammonia production.

Although iron was first smelted 3,500 years ago, its production did not take off until engineer Henry Bessemer, in 1856, developed an economical way to mass-produce steel from iron.

Summary of properties (Fe)

Atomic weight55.845(2)
Discoverer (year)unknown (1774)
Natural formmetallic solid (body centered cubic)
Electron configuration[Ar] 3d6 4s2
Melting point (ºC)1535
Boiling point (ºC)2750
Abundance in earth's crust (ppm)56300
Isotope (abundance)54Fe (5.845), 57Fe (2.119), 58Fe (0.282)
Density g/cm37.87
Van der Waals radius (pm)204
Covalent radius (pm)124
Electronegativity (Pauling)1.88
Vaporization enthalpy (kJ/mol)351.00
Enthalpy of fusion (kJ/mol)13.81
Specific heat capacity (J/g·K) at 25ºC and 1 atm0.45
Thermal conductivity (W/cm·K) at 25ºC and 1 atm0.800
Oxidation state+3, +2
Electron affinity (eV)0.15
1st Ionization potential (eV)7.9024

Back to the Periodic Table of the Elements.