Iron (Fe)

Iron is the most abundant element on Earth by mass, most of it in the core, and the Earth's magnetic field is generated by that molten iron circulating. It is also the end of the line for stellar fusion: iron-56 has the highest binding energy per nucleon of any common nucleus, so fusing it releases no energy and a massive star that reaches an iron core collapses within seconds. The transition from bronze to iron around 1200 BC was less about iron being better — early iron was worse than good bronze — than about iron ore being everywhere while tin was not.

Properties

Atomic number

26

Symbol

Fe

Standard atomic weight

55.845 u

Category

Transition metal

Group

8

Period

4

Block

d-block

Electron configuration

[Ar] 4s² 3d⁶

Electrons per shell

2, 8, 14, 2

Melting point

1,811 K — 1537.8 °C — 2800.1 °F

Boiling point

3,134 K — 2860.8 °C — 5181.5 °F

Density

7.874 g/cm³

Electronegativity

1.83 (Pauling)

Oxidation states

+3, +2

Discovered

Known since antiquity

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶

Noble gas shorthand

[Ar] 4s² 3d⁶

Shells

K: 2 · L: 8 · M: 14 · N: 2

What it is used for

• Steel — buildings, bridges, ships, cars, tools, tin cans
• Cast iron for engine blocks, cookware and manhole covers
• Transformer and motor cores, as electrical steel
• Iron supplements and fortified flour and cereal
• Iron oxide pigments — most reds, browns and yellows in paint

Iron's magnetism disappears above its Curie point of 1,043 K, well below its melting point — a red-hot horseshoe is not magnetic.

Neighbours in the table

Group 8

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Iron sits in group 8 with ruthenium, osmium, hassium.