We use cookies and other tracking technologies to improve your browsing experience on our website, to show you personalized content and targeted ads, to analyze our website traffic, and to understand where our visitors are coming from. For more information, please review our cookie policy and privacy policy.
By choosing I Accept, you consent to our use of cookies and other tracking technologies.

Iron (Fe)

Iron is a chemical element of the periodic table with chemical symbol Fe and atomic number 26 with an atomic weight of 55.8452 u and is classed as transition metal and is part of group 8 (iron group). Iron is solid at room temperature.

Iron in the periodic table

Atomic number26
Group8 (Iron group)
ClassificationTransition Metal
AppearanceLustrous metallic with a grayish tinge
Color Gray
Number of protons26 p+
Number of neutrons30 n0
Number of electrons26 e-
From Wikipedia, the free encyclopediaIron is a chemical element with symbol Fe (from Latin:ferrum) and atomic number 26. It is a metal in the first transition series. It is by mass the most common element on Earth, forming much of Earth's outer and inner core.

Physical properties

Phase at STPSolid
Density7.874 g/cm3
Atomic weight55.8452 u

Thermal properties

Melting point1811 K
1537.85 °C
2800.13 °F
Boiling point3134 K
2860.85 °C
5181.53 °F
Heat of vaporization349.5 kJ/mol

Atomic properties

Electronegativity (Pauling Scale)1.83
Electron affinity14.785 kJ/mol
Oxidation states−4, −2, −1, 0, +1, +2, +3, +4, +5, +6, +7
(an amphoteric oxide)
Ionization energies
  1. 762.5 kJ/mol
  2. 1561.9 kJ/mol
  3. 2957 kJ/mol
  4. 5290 kJ/mol
  5. 7240 kJ/mol
  6. 9560 kJ/mol
  7. 12060 kJ/mol
  8. 14580 kJ/mol
  9. 22540 kJ/mol
  10. 25290 kJ/mol
  11. 28000 kJ/mol
  12. 31920 kJ/mol
  13. 34830 kJ/mol
  14. 37840 kJ/mol
  15. 44100 kJ/mol
  16. 47206 kJ/mol
  17. 122200 kJ/mol
  18. 131000 kJ/mol
  19. 140500 kJ/mol
  20. 152600 kJ/mol
  21. 163000 kJ/mol
  22. 173600 kJ/mol
  23. 188100 kJ/mol
  24. 195200 kJ/mol
  25. 851800 kJ/mol
  26. 895161 kJ/mol

Electron configuration for iron

Electron configuration
Shorthand configuration
[Ar] 3d6 4s2
Electron configuration
Full configuration
1s2 2s2 2p6 3s2 3p6 3d6 4s2
Electron configuration chart
Electrons per shell2, 8, 14, 2
Valence electrons 2 or 8
Valency electrons 2, 3
Bohr model
IronElectron shell for Iron, created by Injosoft ABFe
Figure: Shell diagram of Iron (Fe) atom.
Orbital Diagram

The history of Iron

DiscoveryMiddle East (5000 BC)
Discovery of iron
There is evidence that iron was known from before 5000 BC. The oldest known iron objects used by humans are some beads of meteoric iron, made in Egypt in about 4000 BC. The discovery of smelting around 3000 BC led to the start of the Iron Age around 1200 BC and the prominent use of iron for tools and weapons. However, iron artefacts of great age are much rarer than objects made of gold or silver due to the ease with which iron corrodes. The technology developed slowly, and even after the discovery of smelting it took many centuries for iron to replace bronze as the metal of choice for tools and weapons.


List of unique identifiers for Iron in various chemical registry databases
CAS Number7439-89-6
ChemSpider ID22368
EC number231-096-4
PubChem CID Number23925