Iron underpins steelmaking, where carbon and other additions produce materials with different strengths and uses. It also forms magnetic materials and industrial catalysts. Its tendency to rust in damp air makes a bridge or bicycle a starting point for exploring reactions, protection, and alloy design.
FROM ELEMENT TO APPLICATION
AN ELEMENT IN CONTEXT
Why does identifying iron in a bridge not fully explain the bridge's mechanical performance?
Iron–carbon alloys with selected additions
FOLLOW THIS RELATIONSHIP
Start with structural requirements
A bridge member must carry defined loads within a larger structure, linking the material choice to geometry, connections, and the intended service environment.
Explore the model (optional)
Spatial model
INTERACTIVE 3D54 visible sites
Iron host · a structural referenceDrag to rotate · scroll or pinch to zoom
This body-centered-cubic iron fragment provides a reference for the host material. Steel microstructure, carbon content, phases and processing need a fuller account.
What this representation means
Idealized crystal fragment. Spheres and spacing are schematic; cropped boundary sites have fewer displayed neighbors than interior sites. This is an iron reference lattice, not a prediction of a particular steel microstructure or its strength.
Atomic identity, reference properties and structure models
Loading deposited hemoglobin coordinates…
Loading reference properties…
HISTORY & HUMAN DISCOVERY
A long material history before modern metallurgy
Iron entered human use long before modern elemental names and laboratory definitions. Its durable objects preserve a history of changing metalworking skills, including the celebrated wrought-iron pillar in Delhi. Such artifacts also show that behavior depends on more than the element's name. Composition, processing, structure, and exposure help explain why different iron objects can have very different lives in the environment.
Prehistory
Iron entered human use
Iron was used before a single discoverer or modern discovery date could be recorded.
c. 400 CE
Delhi pillar made
The wrought-iron pillar illustrates sophisticated early metalworking and exceptional preservation.
Iron occurs in stars, meteorites, and terrestrial such as hematite. In living systems, iron-containing molecules also serve important functions, including oxygen transport by hemoglobin. These settings involve different structures and chemical environments, so iron in an , a meteorite, and a should not be treated as the same material.
Iron reacts readily in many environments, and moisture can promote corrosion. Its magnetic behavior depends on structure and temperature, while carbon and other additions alter the properties of iron-based materials. Pure iron, wrought iron, cast iron, and steel therefore describe related but materially different systems.
Each section links its supporting references. Descriptions and diagrams were authored for this atlas. Source checks completed. Source checks dated 2026-09-06.
CITE THIS PAGE
Family labels and the group-3 layout are teaching conventions. A table position does not establish an unknown bulk property. Electronic configurations refer to neutral atoms; ions and material environments require their own account.
1HHO · hemoglobin in three dimensionsDrag to rotate · scroll or pinch to zoom
Four folded protein chains position four iron-containing hemes. Rotate the deposited coordinate model, then isolate a heme to examine the local environment.
What this representation means
RCSB PDB 1HHO, X-ray resolution 2.10 Å. Selected deposited coordinates and biological assembly operators; atom display sizes are exaggerated. Cα connectors indicate sequence continuity, not direct Cα–Cα bonds. Heme connectors use a distance heuristic, not a bond-order assignment. Missing residues are not reconstructed. Oxy/deoxy views are separately centered, not aligned or morphed.
Deposited record 1HHO · revision 2.3, 2026-08-12. Archive coordinates: CC0. Original rendering.
REFERENCE PROPERTIES
Read each reference property together with its units, conditions and the reference information below.
Not yet recorded: electron affinity, second ionization energy, ground-state term symbol, van der waals radius, thermal conductivity, specific heat capacity, electrical resistivity, crystal structure, lattice parameter a, space group, abundance in seawater, abundance in the universe, annual production, supply-risk listing, hazard classification, biological role, cas registry number, pubchem cid, wikidata item. These families are declared and awaiting an ingestion run against the source each names; they are listed here rather than shown as empty rows.
Physical
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Phase at 20 °C
solid
293.15 K, 101.325 kPa
Melting point in K
1811 K
at standard pressure unless noted
Boiling point in K
3134 K
101.325 kPa
Density in g/cm³
7.87 g/cm³
solids and liquids at 293 K; gases at 273 K and 101.325 kPa
Atomic and electronic
Intended reference: Pauling electronegativity scale · Widely tabulated; original in The Nature of the Chemical Bond
Electronegativity in Pauling
1.83 Pauling
Pauling scale
First ionization energy in kJ/mol
762.5 kJ/mol
gas-phase neutral atom, ground state
Covalent radius in pm
132 pm
single-bond covalent radius
Common oxidation states
+2, +3
states met in ordinary compounds; not exhaustive
Occurrence and identity
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Abundance in the crust in mg/kg
56300 mg/kg
upper continental crust, mass fraction
Has stable isotopes
Yesderived
Discovery year
Not recorded
WHERE IT SITS AMONG ITS NEIGHBORS
Electronegativity across period 4
Fe 1.83 Pauling · Iron
Electronegativity across period 4. Exact values.
K
0.82
Ca
1
Sc
1.36
Ti
1.54
V
1.63
Cr
1.66
Mn
1.55
Fe
1.83
Co
1.88
Ni
1.91
Cu
1.9
Zn
1.65
Ga
1.81
Ge
2.01
As
2.18
Se
2.55
Br
2.96
Kr
3
Electronegativity down group 8
Fe 1.83 Pauling · Iron
Electronegativity down group 8. Exact values.
Fe
1.83
Ru
2.2
Os
2.2
The trend uses the same reference-property values as the periodic table. Elements with no recorded value are left out of the line rather than drawn at zero.
