Iron (Fe): Electron Configuration, Properties and Uses
Iron (Fe): Electron Configuration, Properties and Uses
Electron configuration [Ar] 4s2 3d6 · group 8 · period 4 · Ar 55.845
Iron data
- Atomic number
- 26
- Relative atomic mass
- 55.845
- Group
- 8
- Period
- 4
- Block
- d
- Category
- Transition metal
- Electron configuration
- [Ar] 4s2 3d6
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d6
- Electrons per shell
- 2, 8, 14, 2 (K L M N)
- Valence electrons
- 8
- Electronegativity (Pauling)
- 1.83
- First ionisation energy
- 7.902 eV
- Atomic radius (van der Waals)
- 194 pm
- State at room temperature
- Solid
- Melting point
- 1538 °C
- Boiling point
- 2861 °C
- Density
- 7.874 g/cm³
- Common oxidation states
- +3, +2
- Discovered
- ancient times
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2 · L 8 · M 14 · N 2
Orbital diagram (outer electrons)
About iron
Iron, symbol Fe, is element number 26 in the periodic table. It is a transition metal in group 8, period 4, d-block. Iron has been known and used since ancient times. The symbol Fe comes from the Latin ferrum. Iron is a solid at room temperature, melting at 1538 °C and boiling at 2861 °C.
Iron electron configuration
The electron configuration of iron is 1s2 2s2 2p6 3s2 3p6 4s2 3d6, or in short [Ar] 4s2 3d6. Its electrons occupy 4 shells: K = 2, L = 8, M = 14, N = 2. For transition metals, valence electrons are counted from the 4s and 3d subshells: 2 + 6 = 8, matching group 8. When it forms cations, electrons leave the outermost subshell first: Fe2+ = [Ar] 3d6; Fe3+ = [Ar] 3d5.
Filling order: 1s2(2) → 2s2(4) → 2p6(10) → 3s2(12) → 3p6(18) → 4s2(20) → 3d6(26)
Uses of iron
Well-known applications of iron include steel for construction and machinery, haemoglobin that carries oxygen in blood, the Haber process catalyst, and LFP (lithium iron phosphate) battery cathodes. For research and analysis you can browse iron compounds in the AMI Scientific catalogue.
Safety
Iron is fairly safe, though an overdose of iron supplements is dangerous, especially for children. Always read the safety data sheet (SDS) before working with a chemical.
Other elements in group 8
Frequently asked questions
What is the electron configuration of iron?
The electron configuration of iron (Fe, atomic number 26) is 1s2 2s2 2p6 3s2 3p6 4s2 3d6, or [Ar] 4s2 3d6 in short. By shell: 2, 8, 14, 2.
How many valence electrons does iron have?
Iron has 8 valence electrons.
Which group and period is iron in?
Iron is in group 8, period 4, d-block.
What is the atomic mass of iron?
The relative atomic mass of iron is 55.845. Use it to calculate molar mass with the molar mass calculator.
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