26Fe55.845
Iron
Transition metals · solid at STP · Block D
About
Iron is the most common element on Earth by mass and the cornerstone of the modern industrial world, primarily due to its low cost and high strength. It is the main component of steel, the most widely used structural material. In biology, iron is a key component of the hemoglobin molecule in red blood cells, which is responsible for transporting oxygen throughout the body. It is ferromagnetic and rusts easily.
Atomic Properties
Atomic Number26
Atomic Weight55.845 u
Neutrons (common)30
Electron Configuration[Ar] 3d⁶ 4s²
Full Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²
Electrons per Shell2, 8, 14, 2
Electronegativity1.83
Electron Affinity14.785 kJ/mol
Oxidation States+2, +3, +6
Covalent Radius125 pm
Van der Waals Radius184 pm
Ionic Radius78 pm
Periodic Table Position
Group8
Period4
BlockD
Chemical SeriesTransition metals
Physical Properties
State at STPsolid
Appearancelustrous metallic with a grayish tinge
Crystal Structurebcc
Magnetic Orderingferromagnetic
Speed of Sound5,120 m/s
Poisson Ratio0.29
Thermal Properties
Melting Point1,811 K
Boiling Point3,134 K
Triple Point1,811 K
Thermal Expansion12.1 1/K
Thermal Conductivity80.4 W/(m·K)
Specific Heat0.449 J/(g·K)
Molar Heat25.1 J/(mol·K)
Heat of Fusion13.81 kJ/mol
Heat of Vaporization340 kJ/mol
Abundance
In Earth's Crust56,300 ppm
In Ocean0.003 ppm
In Solar System1,400 ppm
In Human Body60 ppm
In Universe1,100 ppm
Discovery
Discovered byAncient civilizations
Discovery YearKnown since antiquity
Occurrenceprimordial
CAS Number7439-89-6
Electron Configuration
Energy
↿⇂
↿⇂
↿⇂
↿⇂
↿⇂
↿⇂
↿⇂
↿⇂
↿⇂
↿⇂
↿⇂
↿
↿
↿
↿
4p
5s
4d
5p
6s
4f
5d
6p
7s
5f
6d
7p
Isotopes of Iron
| Symbol ▲ | Mass (u) ▲ | Abundance ▲ | Half-life ▲ | Decay Mode ▲ |
|---|---|---|---|---|
| 52Fe | 51.948110 | — | 8.275 h | Positron Emission, Electron Capture |
| 54Fe | 53.939610 | 5.845% | Stable | Stable |
| 55Fe | 54.938293 | — | 2.7562 y | Electron Capture |
| 56Fe | 55.934940 | 91.754% | Stable | Stable |
| 57Fe | 56.935390 | 2.119% | Stable | Stable |
| 58Fe | 57.933280 | 0.282% | Stable | Stable |
| 59Fe | 58.934876 | — | 44.50 d | Beta Minus Decay |
| 60Fe | 59.934072 | Trace | 2.62 My | Beta Minus Decay |
Interactive Visualization
Explore the 3D Bohr model of Iron in our interactive viewer.
View 3D Model of Iron