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Chemical element · Atomic number 26
Iron (Fe)
Transition metals · Period 4 · Solid
Element identity
- Atomic number (Z)
- 26
- Symbol
- Fe
- Atomic weight / isotope mass number
- 55.845(2)
- Category
- Transition metals
- Physical state (reference)
- Solid
- Period
- 4
- Group (reference)
- 8
- Block
- d
Physical properties
- Appearance
- Lustrous metallic with a grayish tinge
- Density
- 7.874 g·cm⁻³
- Melting point
- 1811 K / 1538 °C / 2800 °F
- Boiling point
- 3134 K / 2862 °C / 5182 °F
- Sublimation point
- Not available
Atomic and material properties
- Electron configuration
- [Ar] 3d⁶ 4s²
- Electrons per shell
- K2 L8 M14 N2
- Oxidation states
- −4, −2, −1, 1, 2, 3, 4, 5, 6
- Electronegativity (Pauling)
- 1.83
- Atomic radius
- 156 pm
- Covalent radius
- Low spin: 132±3 pm High spin: 152±6 pm
- Molar ionization energies
- 1st: 762.5 kJ·mol⁻¹ 2nd: 1561.9 kJ·mol⁻¹ 3rd: 2957 kJ·mol⁻¹ 4th: 5290 kJ·mol⁻¹ 5th: 7240 kJ·mol⁻¹ 6th: 9560 kJ·mol⁻¹ 7th: 12,060 kJ·mol⁻¹ 8th: 14,580 kJ·mol⁻¹ 9th: 22,540 kJ·mol⁻¹ 10th: 25,290 kJ·mol⁻¹ 11th: 28,000 kJ·mol⁻¹ 12th: 31,920 kJ·mol⁻¹ 13th: 34,830 kJ·mol⁻¹ 14th: 37,840 kJ·mol⁻¹ 15th: 44,100 kJ·mol⁻¹ 16th: 47,206 kJ·mol⁻¹ 17th: 122,200 kJ·mol⁻¹ 18th: 131,000 kJ·mol⁻¹ 19th: 14,0500 kJ·mol⁻¹ 20th: 152,600 kJ·mol⁻¹ 21st: 163,000 kJ·mol⁻¹ 22nd: 173,600 kJ·mol⁻¹ 23rd: 188,100 kJ·mol⁻¹ 24th: 195,200 kJ·mol⁻¹ 25th: 851,800 kJ·mol⁻¹ 26th: 895,161 kJ·mol⁻¹
- Thermal conductivity
- 80.4 W·m⁻¹·K⁻¹
- Molar heat capacity
- 25.10 J·mol⁻¹·K⁻¹
- Crystal structure
- a=286.65 pm: body-centered cubic Between 1185–1667 K: face-centered cubic
- CAS number
- 7439-89-6
Property source: Wikipedia — Iron, adapted from the Nuclides App snapshot. Quoted conditions and qualifiers are retained.
Sources and interpretation
Snapshot exported 24 October 2026 from the element assets used by Nuclides. Properties are a reference compilation, not a new evaluation. Missing values are shown as “Not available”. Density and phase depend on temperature, pressure and allotrope; retained conditions are part of the quoted property.
Atomic weight is dimensionless. Parentheses give uncertainty in the last quoted digits. A single integer in square brackets is an isotope mass number, not a standard atomic weight. The snapshot can differ from current evaluations; consult CIAAW standard atomic weights and the IUPAC periodic table for current values and conventions.
Element properties in the App snapshot are adapted from Wikipedia. Each element page links to its source article; text adaptations are available under CC BY-SA 4.0. No third-party images are included.
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