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
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.
Where Iron sits among the 118 elements
The table compares the reported values for Iron with every other element that carries the same value in the snapshot. A rank is not a judgement, it is orientation: it says how unusual this value is across the periodic table.
| Value | Iron | Position in the data set |
|---|---|---|
| Melting point | 1,811 K | Rank 26 of 103 elements with a reported value. Highest: Carbon. |
| Boiling point | 3,134 K | Rank 38 of 93 elements with a reported value. Highest: Rhenium. |
| Density | 7.874 g/cm³ | Rank 41 of 96 elements with a reported value. Highest: Osmium. |
| Electronegativity (Pauling) | 1.83 | Rank 41 of 95 elements with a reported value. Highest: Fluorine. |
| Ionisation energy | 7.902 eV | Rank 35 of 102 elements with a reported value. Highest: Helium. |
All values and ranks come from the PubChem Periodic Table snapshot, retrieved on 2026-07-15. Elements without a reported value are excluded, so the population differs per row.
The neighbours of Iron in the periodic table
- Place in the table
- Group 8, period 4, D block. Classified as transition metal, solid at standard conditions.
- Direct neighbours
- Atomic number 26. Preceded by Manganese, followed by Cobalt.
- Same group
- Same number of outer electrons, and therefore similar reactivity to Ruthenium, Osmium, Hassium.
- Discovery
- Recorded in the snapshot as: known since antiquity. Who, where and under what circumstances is not part of that record, so this page carries the sourced year and no discovery narrative.
- Oxidation states
- +3, +2. They follow from the electron configuration [Ar]4s2 3d6 and indicate which compounds to expect.
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