ElementsWhat is iron?
Iron is the most used metal on Earth and makes up most of the planet's core. It rusts in damp air. Blood is red because of the iron in haemoglobin, which carries oxygen.
What is iron used for?
Steel for buildings, bridges, railways, ships, vehicles, machines and tools. Also cast iron cookware and magnets.
Where the name comes from
From an Old English word. The symbol Fe comes from ferrum, its Latin name.
Key facts
- Symbol
- Fe
- Atomic number
- 26
- Atomic mass
- 55.84 u
- Family
- Transition metal
- Period
- 4
- Group
- 8
- Block
- d
- State at room temperature
- Solid
- Melting point
- 1,538 °C (1,811 K, 2,800 °F)
- Boiling point
- 2,861 °C (3,134 K, 5,182 °F)
- Density
- 7.87 g/cm³
- Electrons per shell
- 2, 8, 14, 2
- Electron configuration
- [Ar]4s2 3d6
- Common oxidation states
- +3, +2
- Electronegativity (Pauling)
- 1.83
- First ionisation energy
- 7.902 eV
- Electron affinity
- 0.163 eV
- Atomic radius (van der Waals)
- 194 pm
- Discovered
- Known since ancient times
Place in the periodic table
Iron is element number 26. It sits in period 4 (row 4) of the periodic table, in group 8 (column 8), and belongs to the d-block. Just before it comes manganese (25), and just after it comes cobalt (27). In the same column, ruthenium is below it. Elements in one column tend to behave alike.
Family: Transition metals.
Physical properties
At room temperature iron is a solid. It melts at 1,538 °C and boils at 2,861 °C, so it stays liquid over a range of 1,323 degrees. Its density is 7.87 grams per cubic centimetre, so a one-litre block would weigh about 7.87 kilograms. By density it ranks 41st among the 96 elements with a measured value.
Inside the atom
An atom of iron has 26 protons in its nucleus and, when neutral, 26 electrons around it. The electrons are arranged in 4 shells: 2, 8, 14, 2. The outermost shell holds 2 electrons. Written in full, the electron configuration is [Ar]4s2 3d6.
Its electronegativity on the Pauling scale is 1.83. This number shows how strongly an atom pulls shared electrons towards itself: fluorine, the strongest, is 3.98. Removing one electron from an atom takes 7.902 electronvolts (about 762 kilojoules per mole). One mole of iron weighs 55.84 grams, so a single gram contains about 1.08 × 1022 atoms.
The ring picture is a simple model that only counts the electrons in each shell. Real atoms do not look like this.
Next steps
- Work out the weight of a compound that contains iron with the molar mass calculator.
- Compare it with every other element in the sortable list.
- Test yourself with the symbol quiz.
Figures on this page are from PubChem (U.S. National Library of Medicine), as downloaded on 11 November 2026. See About and data sources.