Iron (Fe) – element 26
Iron is a chemical element with the symbol Fe and atomic number 26. It is a transition metal in group 8, period 4 of the periodic table (d-block), and is a solid at room temperature.
Iron (Fe) has atomic number 26, atomic mass 55.845 u and electron configuration [Ar] 3d6 4s2.
Iron facts
| Symbol | Fe |
|---|---|
| Atomic number | 26 |
| Atomic mass | 55.845 u (g/mol) |
| Category | transition metal |
| Group | group 8 |
| Period | 4 |
| Block | d-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d6 |
| Noble-gas notation | [Ar] 3d6 4s2 |
| Electrons per shell | 2, 8, 14, 2 |
Bohr model and shells
Iron has 26 electrons in 4 shells: 2, 8, 14, 2. Full configuration and noble-gas notation are in the table; work out any element or ion with the electron configuration calculator.
Physical and atomic properties
| Melting point | 1811 K (1537.8 °C) |
|---|---|
| Boiling point | 3134 K (2860.8 °C) |
| Density | 7.874 g/cm³ |
| Electronegativity (Pauling) | 1.83 |
| Electron affinity | 14.785 kJ/mol |
| Ionization energies | 762.5, 1561.9, 2957 kJ/mol (1st, 2nd, 3rd) |
| Molar heat capacity | 25.1 J/(mol·K) |
| Discovered by | 5000 BC |
Use the atomic mass in the molar mass calculator for any formula containing Fe.
Position in the periodic table
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Frequently asked questions
What is the atomic mass of iron?
The atomic mass of iron is 55.845 u, so one mole of iron atoms weighs 55.845 g.
What is the electron configuration of iron?
Iron has 26 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶, or [Ar] 3d⁶ 4s² in noble-gas notation. Electrons per shell: 2, 8, 14, 2.
Is iron a metal?
Yes. Iron is a transition metal.
Where is iron on the periodic table?
Iron is in group 8, period 4, in the d-block.
Data: Periodic-Table-JSON (CC BY-SA 3.0); standard atomic weights from IUPAC (abridged). Values in brackets are the mass number of the longest-lived isotope.