Chemical element · Atomic number 26
Iron
Iron in the periodic table: atomic number 26, electron configuration, atomic mass, physical data, oxidation states, media credit and visible sources.
Transition metal
solid
55.84 u
Documented element sampleDocumented pieces of elemental iron.
Image credit: W. Oelen
Auto-oriented, limited to 1600 × 1200 pixels and re-encoded as WebP; the subject was not altered.
Atomic classification
Shell occupancy
Iron in the Bohr shell model
This shows the electron distribution of the neutral atom in a simplified shell model.
- K · n=1
- 2 electrons
- L · n=2
- 8 electrons
- M · n=3
- 14 electrons
- N · n=4
- 2 electrons
- Electron configuration
- [Ar]4s2 3d6
- Electrons per shell
- 2 · 8 · 14 · 2
- Group
- 8
- Period
- 4
- Block
- D
- Element category
- Transition metal
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Physical and chemical properties
- Atomic mass
- 55.84 u
- Standard state
- solid
- Density
- 7.874 g/cm³
- Melting point
- 1,811 K
- Boiling point
- 3,134 K
- Electronegativity
- 1.83 (Pauling)
- First ionisation energy
- 7.902 eV
- Oxidation states
- +3, +2
- Discovery
- known since antiquity
Safety and periodic classification
Safety
Safe handling cannot be inferred from Iron's position in the periodic table alone. Laboratory, classroom and disposal decisions must follow the documentation for the exact material and its safety data sheet.
Position and comparison
Iron is in period 4, group 8 and the D block. Its direct neighbours by atomic number are Manganese and Cobalt. The recorded Pauling electronegativity is 1.83. Periodic trends are compared only through the separately sourced neighbouring values.
Sources and scope
PubChem attributes element data to sources including IUPAC, NIST and IAEA. Quanta stores the referenced snapshot locally and leaves unknown values unavailable.