Iron (Fe, atomic number 26): properties, occurrence, and uses

Properties

Iron is a silvery-gray, lustrous metal in its pure form. As a chemical element it shows ferromagnetism at normal temperatures and becomes non-magnetic above its Curie temperature. Pure iron is relatively soft compared with many industrial alloys, but it can be made much stronger when combined with carbon and other elements to form materials such as steel. Iron reacts with oxygen and water to form iron oxides (rust), which affects its durability in outdoor environments.

Occurrence and sources

• Most of Earth's iron is sequestered in the planet's core, where it exists in dense metallic form.
• In the crust, iron is found chiefly as oxides and sulfides—minerals that are mined as iron ore for industrial use.
• Meteoric iron, which predates smelting, was used by some ancient cultures because it arrived in a metallic state.

Uses

Iron is widely used because it combines useful mechanical properties with low cost. The majority of manufactured iron is converted into steel, an alloy that dominates construction, transportation, and machinery. Other applications include cast iron products, tools, and components where toughness and wear resistance are required.

History

People began producing and working iron from ores in different regions at varying times; around 1200 BCE iron working became common enough in some areas that historians mark a shift from the Bronze Age to the Iron Age. Earlier, naturally occurring metallic iron from meteorites had been used by humans.

Biological role

Iron is an essential element for most living organisms. In many animals it is a central component of hemoglobin and other proteins involved in oxygen transport and cellular respiration. Both iron deficiency and iron excess can cause health problems, so biological systems tightly regulate iron levels.