Periodic Table


Atomic number: 26
Atomic weight: 55.845
Symbol: Fe
Group number: 8
Electronic configuration: [Ar].3d6.4s2


Iron is a relatively abundant element in the universe. It is found in the sun and many types of stars in considerable quantity. Iron nuclei are very stable. Iron is a vital constituent of plant and animal life, and is the key component of haemoglobin.

The pure metal is not often encountered in commerce, but is usually alloyed with carbon or other metals. The pure metal is very reactive chemically, and rapidly corrodes, especially in moist air or at elevated temperatures. Any car owner knows this. Iron metal is a silvery, lustrous metal which has important magnetic properties.

General information

Discoveror: Known since ancient times
Date discovered:
Discovered at: not known
Meaning of name: From the Anglo-Saxon word "iron" (the origin of the symbol Fe comes from the Latin word "ferrum") meaning "iron"

Physical data

Standard state: solid at 298 K
Colour: lustrous, metallic, greyish tinge
Density of solid at ambient temperature/kg m-3: 7874
Molar volume/cm3: 7.09

Radii /pm

Atomic: 156
Covalent (single bond):
Pauling radius for the ion [Fe]-: no data

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius136.6no data38.2no data


Both values are quoted on the Pauling scale.

Pauling: 1.83
Allred Rochow: 1.64

Crystal Structure

structure: bcc (body-centred cubic)

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.


Temperatures (/K)

melting point: 1811
boiling point: 3134

Enthalpies /kJ mol-1

fusion: 13.8
vaporization: 345

single bond enthalpies:
Fe-F Fe-Cl Fe-Br Fe-I Fe-Fe
no data no data no data 339.7 100

Ionization enthalpies /kJ mol-1

Number Enthalpy


This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance
54Fe53.9396127 (15)5.8 (1)
56Fe55.9349393 (16)91.72 (30)
57Fe56.9353958 (16)2.2 (1)
58Fe57.9332773 (16)0.28 (1)

Further Information

Copyright 1997 Mark Winter
Department of Chemistry at the University of Sheffield, Sheffield S3 7HF, England.

The current version of this document is at http://www.shef.ac.uk/~chem/web-elements-I/Fe.html