026Transition metal · Group 8 · Period 4
Iron
Iron (Fe) is element 26, a transition metal in the d-block — group 8, period 4. It is a solid at room temperature with 4 electron shells (2, 8, 14, 2) and an atomic mass of 55.8452 u.
- Atomic mass
- 55.85 u
- Phase · STP
- solid
- Melting
- 1811 K · 1538 °C
- Boiling
- 3134 K · 2861 °C
- Electronegativity
- 1.83
- Density
- 7.874 g/cm³
Photograph — Chemical ELements A Virtual Museum, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0> source: https://images-of-elements.com/iron.php
Emission spectrum
The visible light Iron emits when energised — its unique spectral fingerprint.
Identity
- Atomic number
- 26
- Standard atomic weight
- 55.85 u
- Category
- Transition metal
- Group
- 8
- Period
- 4
- Block
- d-block
- Oxidation states
- +3, +2
Physical properties
- Melting point
- 1811 K · 1538 °C
- Boiling point
- 3134 K · 2861 °C
- Density
- 7.874 g/cm³
- Molar heat capacity
- 25.1 J/(mol·K)
- Atomic radius
- 194 pm
- Electron affinity
- 14.785 kJ/mol
Atomic structure
26protons
30neutrons
26electrons
2valence e⁻
- Noble-gas notation
- [Ar] 3d6 4s2
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d6
- Electrons per shell
- 2, 8, 14, 2
Periodic trends
Where Iron ranks across all 118 elements.
Ionization energies
Energy to remove each successive electron (kJ/mol).
762.51
1.6k2
3.0k3
5.3k4
7.2k5
9.6k6
12.1k7
14.6k8
22.5k9
25.3k10
Successive ionization energies (kJ/mol, log scale).
Discovery
- Discovered
- Ancient
- Discovered by
- 5000 BC
- Named by
- —
- Appearance
- lustrous metallic with a grayish tinge