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26 Fe Iron 55.845

Transition metal

Iron 铁

[Ar] 3d⁶ 4s²

  • Period 4
  • Group 8
  • Block d
  • Solid

Electron configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²

Orbital diagram (valence)

3d ↑↓↑↑↑↑
4s ↑↓
Electrons per shell
2, 8, 14, 2
Unpaired electrons
4
Zeff (Slater)
3.75

Properties

Atomic weight
55.845
Electronegativity (Pauling)
1.83
First ionization energy
762.4 kJ/mol
Electron affinity
15.73 kJ/mol
Covalent radius
132 pm
van der Waals radius
194 pm
Melting point
1811 K
Boiling point
3134 K
Density
7.874 g/cm³
Melting / boiling point
1537.8 °C / 2860.8 °C
Common oxidation states
+3, +2
Discovered
Known since antiquity

Natural isotopes

Mass number AAbundance
54Fe5.85 %
56Fe91.75 %
57Fe2.12 %
58Fe0.2820 %

Isotope masses: AME2020; abundances: IUPAC/CIAAW representative values.

Iron in the course

The lessons that discuss this element most (ranked by mentions).

Lab experiments with Iron

Standard reduction potentials

FeOX4X2−(aq)+8 HX+(aq)+3 eX−→FeX3+(aq)+4 HX2O(l)\ce{FeO4^2-(aq)} + \ce{8H+(aq)} + \ce{3e-} \mathrel{\ce{->}} \ce{Fe^3+(aq)} + \ce{4H2O(l)}+2.200 V
FeX3+(aq)+eX−→FeX2+(aq)\ce{Fe^3+(aq)} + \ce{e-} \mathrel{\ce{->}} \ce{Fe^2+(aq)}+0.771 V
[Fe(CN)X6]X3−(aq)+eX−→[Fe(CN)X6]X4−(aq)\ce{[Fe(CN)6]^3-(aq)} + \ce{e-} \mathrel{\ce{->}} \ce{[Fe(CN)6]^4-(aq)}+0.358 V
FeX3+(aq)+3 eX−→Fe(s)\ce{Fe^3+(aq)} + \ce{3e-} \mathrel{\ce{->}} \ce{Fe(s)}−0.037 V
FeX2+(aq)+2 eX−→Fe(s)\ce{Fe^2+(aq)} + \ce{2e-} \mathrel{\ce{->}} \ce{Fe(s)}−0.447 V
Fe(OH)X3(s)+eX−→Fe(OH)X2(s)+OHX−(aq)\ce{Fe(OH)3(s)} + \ce{e-} \mathrel{\ce{->}} \ce{Fe(OH)2(s)} + \ce{OH-(aq)}−0.560 V
All potentials

Crystal structures

  • Fe\ce{Fe} Body-centred cubic lattice parameter a = 286.6 pm
View in the crystal atlas

Periodic trend

H: 1312 kJ/molHe: 2372 kJ/molLi: 520.2 kJ/molBe: 899.5 kJ/molB: 800.6 kJ/molC: 1086 kJ/molN: 1402 kJ/molO: 1314 kJ/molF: 1681 kJ/molNe: 2081 kJ/molNa: 495.8 kJ/molMg: 737.7 kJ/molAl: 577.6 kJ/molSi: 786.5 kJ/molP: 1012 kJ/molS: 999.6 kJ/molCl: 1251 kJ/molAr: 1521 kJ/molK: 418.8 kJ/molCa: 589.8 kJ/molSc: 633 kJ/molTi: 658.8 kJ/molV: 650.9 kJ/molCr: 652.9 kJ/molMn: 717.3 kJ/molFe: 762.4 kJ/molCo: 760.4 kJ/molNi: 737.1 kJ/molCu: 745.4 kJ/molZn: 906.4 kJ/molGa: 578.8 kJ/molGe: 762.2 kJ/molAs: 947 kJ/molSe: 940.9 kJ/molBr: 1140 kJ/molKr: 1351 kJ/molRb: 403 kJ/molSr: 549.5 kJ/molY: 599.8 kJ/molZr: 640.1 kJ/molNb: 652.1 kJ/molMo: 684.3 kJ/molTc: 702.4 kJ/molRu: 710.2 kJ/molRh: 719.7 kJ/molPd: 804.4 kJ/molAg: 731 kJ/molCd: 867.8 kJ/molIn: 558.3 kJ/molSn: 708.6 kJ/molSb: 833.6 kJ/molTe: 869.3 kJ/molI: 1008 kJ/molXe: 1170 kJ/molCs: 375.7 kJ/molBa: 502.9 kJ/mol 0510152025303540455055Atomic number Z05001000150020002500First ionization energy / kJ/mol

Group 8

Data: PubChem periodic table (public domain); atomic weights are IUPAC abridged standard values; covalent radii from Cordero et al. (2008).