Iron (Fe)
Ferrum
Iron (Fe) is a transition metal in period 4, group 8. Its relative atomic mass is 55.845 and the molar mass of the atom is 55.845 g/mol.
Atomic number 26
Atomic mass 55.845
Molar mass 55.845 g/mol
Category Transition metal Solid
Properties of iron
| Atomic number | 26 |
|---|---|
| Symbol | Fe |
| Latin name | Ferrum |
| Relative atomic mass | 55.845 |
| Molar mass | 55.845 g/mol |
| Group, period, block | 8, 4, d |
| Category | Transition metal |
| State at 20 °C | Solid |
| Electron configuration | [Ar] 3d⁶ 4s² |
| Valency / oxidation states | II, III / +2, +3 |
| Electronegativity (Pauling) | 1.83 |
| Melting / boiling point | 1538 °C / 2862 °C |
| Density | 7.874 g/cm³ |
| Atomic radius | 140 pm |
| Discovered | antiquity |
Electron configuration of iron
Electrons per shell
K2L8M14N2
Full notation
1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²
Noble-gas notation
26 protons · 26 electrons[Ar] 3d⁶ 4s²
Formula and compounds of iron
Simple substanceFeironMolar mass of Fe: 55.845 g/mol
Oxides- FeOiron(II) oxide
- Fe₂O₃iron(III) oxide
- Fe₃O₄magnetite
- FeCl₃iron(III) chloride
- FeSO₄iron(II) sulfate
- Fe(OH)₃iron(III) hydroxide
Interesting facts about iron
- 1The most common element on Earth by mass — the planet’s core is mostly iron.
- 2Haemoglobin in your blood contains iron, which carries oxygen.
- 3Pure iron is soft; a little carbon turns it into strong steel.
Uses of iron
- Steel and cast iron for construction
- Cars, bridges and tools
- Magnets and transformer cores
- Catalyst in the Haber process
Chemistry not clicking? Try a lesson with a tutor
1-to-1 online chemistry lessons for KS3, GCSE and A-level. Your first lesson is a free trial.
Frequently asked questions
The relative atomic mass of iron is 55.845, so the molar mass of the atom is 55.845 g/mol.
Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s². Noble-gas notation: [Ar] 3d⁶ 4s².
Valency: II, III. Oxidation states: +2, +3.