Structure
Not a diagram of dots on rings — a Monte-Carlo sample of the actual probability density |ψ|² for each occupied subshell. Drag to rotate. Blue and violet mark opposite signs of the wavefunction, which is what makes bonding possible.
Measured values
Every bar shows where iron sits among all 118 elements for that property.
Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.
Size, to scale
Radius 126 pm — that is 0.126 nm, so about 3968 million of them side by side would span a millimetre.
Thermal range
Iron is liquid over a 1323 K window, from 1811 K to 3134 K.
The story
Iron is the element that built civilization and flows through your veins. This mighty metal forms the core of our planet, creates the magnetic field that protects us from cosmic radiation, and literally gives your blood its red color. From ancient Damascus steel swords to modern skyscrapers, iron has been humanity's go-to metal for over 3,000 years. The Iron Age revolutionized human society, enabling everything from agriculture to warfare. In your body, iron atoms sit at the heart of hemoglobin molecules, grabbing oxygen in your lungs and delivering it to every cell. Without iron, your blood couldn't carry oxygen, and you'd suffocate even while breathing. Earth's inner core is a solid ball of iron the size of the moon, spinning slightly faster than the planet itself and generating our protective magnetic shield.
Humanity's first encounter with iron came from the heavens as meteorites containing metallic iron-nickel alloys:
The transition from Bronze Age to Iron Age represents one of humanity's greatest technological leaps:
Iron technology spread rapidly and transformed human civilization across the globe:
Greek and Roman engineers pushed iron technology to new heights:
Medieval Europe revolutionized iron production with mechanical innovations:
Abraham Darby's breakthrough in 1709 transformed iron production for very long periods:
The Industrial Revolution created unprecedented demand for iron and significant production methods:
Henry Bessemer's 1856 invention of the Bessemer process created the steel age:
Modern metallurgy brought scientific understanding to iron production:
Modern iron and steel production became the foundation of global civilization:
Iron's discovery and development represents humanity's greatest technological achievement:
Applications
Iron-based steel production represents humanity's most important industrial process, consuming over 98% of global iron production and forming the skeleton of modern civilization:
Iron and steel enable all forms of modern transportation:
Industrial machinery depends entirely on iron-based materials:
Modern cities and infrastructure are impossible without iron:
High-performance iron alloys enable cutting-edge technology:
Iron-based materials are essential for national security:
Medical applications utilize iron's unique properties:
Energy infrastructure relies fundamentally on iron:
Iron cookware and kitchen tools have been essential for thousands of years:
Residential construction relies heavily on iron-based materials:
Cars, trucks, and motorcycles are fundamentally made from iron and steel:
Iron is absolutely essential for human health:
Athletic equipment and recreational activities depend on iron-based materials:
Yard work and gardening rely on iron tools and materials:
Iron's magnetic properties enable countless everyday applications:
Workplace environments are filled with iron-based products:
Creative applications utilize iron's workability and strength:
Keeping things working requires iron-based tools and parts:
Where it comes from
56300 mg/kg of Earth's crust · more abundant than 97% of elements
Iron is forged in the nuclear furnaces of massive stars and represents the end point of stellar nucleosynthesis:
Earth's core contains 80% of the planet's iron and creates our protective magnetic field:
Iron comprises 5.6% of Earth's crust in various mineral forms that humans have exploited for millennia:
Global iron ore production comes from several world-class geological provinces:
Dissolved iron occurs naturally in various aquatic environments with complex chemistry:
Living organisms actively participate in Earth's iron cycle through various mechanisms:
Banded iron formations (BIFs) tell the story of early Earth's atmosphere and evolution of life:
Iron occurs in diverse geological settings reflecting various formation processes:
Human activities have dramatically altered natural iron cycling processes:
Iron occurs throughout the solar system and provides clues about planetary formation:
Handling
Iron is absolutely essential for human health but requires careful balance to avoid deficiency or toxicity:
Working with iron and steel requires comprehensive safety protocols:
Iron and steel welding presents specific health and safety challenges:
Excessive iron accumulation can cause serious health problems:
Common iron-containing household items require basic safety awareness:
Iron in the environment generally poses minimal risks but requires monitoring:
Working with iron compounds in research settings requires specific precautions:
Medical uses of iron require careful monitoring and dosing:
Iron and steel in construction must meet strict safety standards:
Multiple agencies regulate iron exposure across different sectors:
Quick answers
Iron (symbol Fe) is element 26 on the periodic table, a transition metal in period 4, group 8. The most common element on Earth by mass, the endpoint of stellar fusion, and the metal that named an age. At room temperature it is a solid.
[Ar] 3d⁶ 4s², giving 4 occupied shells holding 2, 8, 14, 2 electrons respectively.Iron melts at 1811 K (1537.9 °C) and boils at 3134 K (2860.9 °C).
The standard atomic weight of Iron is 55.845 u. That is a weighted average across its naturally occurring isotopes, which is why it is rarely a whole number.
Iron has a density of 7.874 g/cm³. Water is 1.0 g/cm³, so a block of iron is about 7.9× heavier.
Iron has a Pauling electronegativity of 1.83. The scale runs from 0.70 (francium, the least greedy for electrons) to 3.98 (fluorine, the most). Values in this middle band tend to form covalent rather than strongly ionic bonds.
Iron has been known since antiquity — it occurs in a form usable without smelting, so no single person can be credited with its discovery. The name comes from anglo-Saxon iren; symbol from Latin ferrum.
Iron makes up about 5.63% of the Earth's crust — one of the most abundant elements there is.