Iron (Fe)

Silvery malleable and ductile metallic transition element. Has nine isotopes and is the fourth most abundant element in the earth's crust. Required by living organisms as a trace element (used in hemoglobin in humans.) Quite reactive, oxidizes in moist air, displaces hydrogen from dilute acids and combines with nonmetallic elements.

Atomic Number	26
Atomic Weight	55.845
Mass Number	56

Group	8
Period	4
Block	d

Protons	26 p⁺
Neutrons	30 n⁰
Electrons	26 e^-

Properties

Energy
Atomic Radius	140 pm 237 pm
Molar Volume	7.1 cm³/mol
Covalent Radius	116 pm 109 pm 102 pm 140 pm 142 pm
Metallic Radius	117 pm 126 pm
Ionic Radius	63 pm 64 pm 61 pm 78 pm 92 pm 49 pm 58 pm 55 pm 64.5 pm 78 pm 58.5 pm 25 pm
Crystal Radius	77 pm 78 pm 75 pm 92 pm 106 pm 63 pm 72 pm 69 pm 78.5 pm 92 pm 72.5 pm 39 pm
Van der Waals Radius	205 pm 204 pm 223 pm 291.2 pm
Density	7.87 g/cm³ 6,980 kg/m³
Proton Affinity	754 kJ/mol
Electron Affinity	0.151 eV/particle
Ionization Energy	7.9024678 eV/particle 16.1992 eV/particle 30.651 eV/particle 54.91 eV/particle 75 eV/particle 98.985 eV/particle 125 eV/particle 151.06 eV/particle 233.6 eV/particle 262.1 eV/particle 290.9 eV/particle 330.81 eV/particle 361 eV/particle 392.2 eV/particle 456.2 eV/particle 489.312 eV/particle 1,262.7 eV/particle 1,357.8 eV/particle 1,460 eV/particle 1,575.6 eV/particle 1,687 eV/particle 1,798.43 eV/particle 1,950.4 eV/particle 2,045.759 eV/particle 8,828.1875 eV/particle 9,277.681 eV/particle

Heat of Vaporization	340 kJ/mol
Heat of Fusion	13.8 kJ/mol
Heat of Formation	415.5 kJ/mol
Electrons
Electron Shells	2, 8, 14, 2

Valence Electrons	2
Electron Configuration	[Ar] 3d⁶ 4s²

Oxidation States	-4, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7
Electronegativity	10.64 eV/particle 0.1392532 1.83
Electrophilicity	1.045904228706801 eV/particle
Phases
Phase	Solid
Gas Phase
Boiling Point	3,134.15 K
Melting Point	1,811.15 K
Critical Pressure
Critical Temperature	9,340.15 K
Triple Point
Visual
Color	Gray #ffa500 #e06633 #e06633
Appearance	lustrous metallic with a grayish tinge
Refractive Index
Thermodynamic Properties
Thermal Conductivity	80.4 W/(m K)
Thermal Expansion	0.0000118 1/K
Molar Heat Capacity	25.1 J/(mol K)
Specific Heat Capacity	0.449 J/(g⋅K)
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
Type	Conductor
Electrical Conductivity	10 MS/m
Electrical Resistivity	0.00000009700000000001 m Ω
Superconducting Point
Magnetism
Type	ferromagnetic
Magnetic Susceptibility (Mass)
Magnetic Susceptibility (Molar)
Magnetic Susceptibility (Volume)
Magnetic Ordering
Curie Point	1,043 K
Neel Point
Structure
Crystal Structure	Body Centered Cubic (BCC)
Lattice Constant	2.87 Å
Lattice Angles	π/2, π/2, π/2
Mechanical Properties
Hardness	490 MPa 4 MPa 608 MPa
Bulk Modulus	170 GPa
Shear Modulus	82 GPa
Young Modulus	211 GPa
Poisson Ratio	0.29
Speed of Sound	4,910 m/s
Classification
Category	Transition metals, Transition metals
CAS Group	VIIIA
IUPAC Group	VIII
Glawe Number	71
Mendeleev Number	59
Pettifor Number	61
Geochemical Class	major
Goldschmidt Class	siderophile
Other
Gas Basicity	731.1 kJ/mol
Dipole Polarizability	62 ± 4 a₀
C6 Dispersion Coefficient	482 a₀ 548 a₀
Allotropes
Neutron Cross Section	2.56
Neutron Mass Absorption	0.0015
Quantum Numbers	5D4
Space Group	229 (Im_3m)

Isotopes of Iron

Stable Isotopes	4
Unstable Isotopes	28
Radioactive Isotopes	28

⁴⁵Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	45.015467 ± 0.000304 Da
Mass Number	45
G-Factor
Half Life	2.5 ± 0.2 ms
Spin	3/2
Quadrupole Moment
Discovery Year	1996
Parity	+

⁴⁵Fe Decay Modes

Decay Mode	Intensity
2p (2-proton emission)	70%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	30%
β⁺ p (β⁺-delayed proton emission)	18.9%
2p (2-proton emission)	7.8%

⁴⁶Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	46.001299 ± 0.000322 Da
Mass Number	46
G-Factor	0
Half Life	13 ± 2 ms
Spin	0
Quadrupole Moment	0
Discovery Year	1992
Parity	+

⁴⁶Fe Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺ p (β⁺-delayed proton emission)	78.7%
2p (2-proton emission)	%

⁴⁷Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	46.992346 ± 0.000537 Da
Mass Number	47
G-Factor
Half Life	21.9 ± 0.2 ms
Spin	7/2
Quadrupole Moment
Discovery Year	1992
Parity	-

⁴⁷Fe Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺ p (β⁺-delayed proton emission)	88.4%

⁴⁸Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	47.980667 ± 0.000099 Da
Mass Number	48
G-Factor	0
Half Life	45.3 ± 0.6 ms
Spin	0
Quadrupole Moment	0
Discovery Year	1987
Parity	+

⁴⁸Fe Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺ p (β⁺-delayed proton emission)	15.3%

⁴⁹Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	48.973429 ± 0.000026 Da
Mass Number	49
G-Factor
Half Life	64.7 ± 0.3 ms
Spin	7/2
Quadrupole Moment
Discovery Year	1970
Parity	-

⁴⁹Fe Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺ p (β⁺-delayed proton emission)	56.7%

⁵⁰Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	49.962988 ± 0.000009 Da
Mass Number	50
G-Factor	0
Half Life	152 ± 0.6 ms
Spin	0
Quadrupole Moment	0
Discovery Year	1977
Parity	+

⁵⁰Fe Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺ p (β⁺-delayed proton emission)	0%

⁵¹Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	50.956855137 ± 0.000001501 Da
Mass Number	51
G-Factor
Half Life	305.4 ± 2.3 ms
Spin	5/2
Quadrupole Moment
Discovery Year	1972
Parity	-

⁵¹Fe Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

⁵²Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	51.948113364 ± 0.000000192 Da
Mass Number	52
G-Factor	0
Half Life	8.275 ± 0.008 h
Spin	0
Quadrupole Moment	0
Discovery Year	1948
Parity	+

⁵²Fe Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

⁵³Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	52.945305629 ± 0.000001792 Da
Mass Number	53
G-Factor	-0.18571428571429 ± 0.0028571428571429
Half Life	8.51 ± 0.02 m
Spin	7/2
Quadrupole Moment
Discovery Year	1938
Parity	-

⁵³Fe Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

⁵⁴Fe

Abundance	5.845 ± 0.105
Relative Atomic Mass	53.939608189 ± 0.000000368 Da
Mass Number	54
G-Factor	0
Half Life
Spin	0
Quadrupole Moment	0
Discovery Year	1923
Parity	+

⁵⁴Fe Decay Modes

Decay Mode	Intensity
2β⁺ (double β⁺ decay)	%

⁵⁵Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	54.938291158 ± 0.00000033 Da
Mass Number	55
G-Factor
Half Life	2.7562 ± 0.0004 y
Spin	3/2
Quadrupole Moment
Discovery Year	1939
Parity	-

⁵⁵Fe Decay Modes

Decay Mode	Intensity
ϵ (electron capture)	100%

⁵⁶Fe

Abundance	91.754 ± 0.106
Relative Atomic Mass	55.934935537 ± 0.000000287 Da
Mass Number	56
G-Factor	0
Half Life
Spin	0
Quadrupole Moment	0
Discovery Year	1923
Parity	+

⁵⁷Fe

Abundance	2.119 ± 0.029
Relative Atomic Mass	56.93539195 ± 0.000000287 Da
Mass Number	57
G-Factor
Half Life
Spin	1/2
Quadrupole Moment	0
Discovery Year	1935
Parity	-

⁵⁸Fe

Abundance	0.282 ± 0.012
Relative Atomic Mass	57.933273575 ± 0.000000339 Da
Mass Number	58
G-Factor	0
Half Life
Spin	0
Quadrupole Moment	0
Discovery Year	1935
Parity	+

⁵⁹Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	58.934873492 ± 0.000000354 Da
Mass Number	59
G-Factor	-0.22386666666667 ± 0.00026666666666667
Half Life	44.5 ± 0.012 d
Spin	3/2
Quadrupole Moment
Discovery Year	1938
Parity	-

⁵⁹Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

⁶⁰Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	59.934070249 ± 0.000003656 Da
Mass Number	60
G-Factor	0
Half Life	2.62 ± 0.04 My
Spin	0
Quadrupole Moment	0
Discovery Year	1957
Parity	+

⁶⁰Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

⁶¹Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	60.936746241 ± 0.0000028 Da
Mass Number	61
G-Factor
Half Life	5.98 ± 0.06 m
Spin	3/2
Quadrupole Moment
Discovery Year	1957
Parity	-

⁶¹Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

⁶²Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	61.936791809 ± 0.000003 Da
Mass Number	62
G-Factor	0
Half Life	68 ± 2 s
Spin	0
Quadrupole Moment	0
Discovery Year	1975
Parity	+

⁶²Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

⁶³Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	62.940272698 ± 0.000004618 Da
Mass Number	63
G-Factor
Half Life	6.1 ± 0.6 s
Spin	5/2
Quadrupole Moment
Discovery Year	1980
Parity	-

⁶³Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

⁶⁴Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	63.940987761 ± 0.000005386 Da
Mass Number	64
G-Factor	0
Half Life	2 ± 0.2 s
Spin	0
Quadrupole Moment	0
Discovery Year	1980
Parity	+

⁶⁴Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

⁶⁵Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	64.945015323 ± 0.000005487 Da
Mass Number	65
G-Factor
Half Life	805 ± 10 ms
Spin	1/2
Quadrupole Moment	0
Discovery Year	1980
Parity	-

⁶⁵Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	%

⁶⁶Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	65.946249958 ± 0.0000044 Da
Mass Number	66
G-Factor	0
Half Life	467 ± 29 ms
Spin	0
Quadrupole Moment	0
Discovery Year	1985
Parity	+

⁶⁶Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	%

⁶⁷Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	66.95093 ± 0.0000041 Da
Mass Number	67
G-Factor
Half Life	394 ± 9 ms
Spin	1/2
Quadrupole Moment	0
Discovery Year	1985
Parity	-

⁶⁷Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	%

⁶⁸Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	67.952875 ± 0.000207 Da
Mass Number	68
G-Factor	0
Half Life	188 ± 4 ms
Spin	0
Quadrupole Moment	0
Discovery Year	1985
Parity	+

⁶⁸Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	0%

⁶⁹Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	68.957918 ± 0.000215 Da
Mass Number	69
G-Factor
Half Life	162 ± 7 ms
Spin	1/2
Quadrupole Moment	0
Discovery Year	1992
Parity	-

⁶⁹Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

⁷⁰Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	69.960397 ± 0.000322 Da
Mass Number	70
G-Factor	0
Half Life	61.4 ± 0.7 ms
Spin	0
Quadrupole Moment	0
Discovery Year	1997
Parity	+

⁷⁰Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	%

⁷¹Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	70.965722 ± 0.000429 Da
Mass Number	71
G-Factor
Half Life	34.3 ± 2.6 ms
Spin	7/2
Quadrupole Moment
Discovery Year	1997
Parity	+

⁷¹Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

⁷²Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	71.968599 ± 0.000537 Da
Mass Number	72
G-Factor	0
Half Life	17 ± 1 ms
Spin	0
Quadrupole Moment	0
Discovery Year	1997
Parity	+

⁷²Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

⁷³Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	72.974246 ± 0.000537 Da
Mass Number	73
G-Factor
Half Life	12.9 ± 1.6 ms
Spin	7/2
Quadrupole Moment
Discovery Year	2010
Parity	+

⁷³Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

⁷⁴Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	73.977821 ± 0.000537 Da
Mass Number	74
G-Factor	0
Half Life	5 ± 5 ms
Spin	0
Quadrupole Moment	0
Discovery Year	2010
Parity	+

⁷⁴Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

⁷⁵Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	74.984219 ± 0.000644 Da
Mass Number	75
G-Factor
Half Life
Spin	9/2
Quadrupole Moment
Discovery Year	2013
Parity	+

⁷⁵Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

⁷⁶Fe

Abundance	Radioactive ☢️
Relative Atomic Mass	75.988631 ± 0.000644 Da
Mass Number	76
G-Factor	0
Half Life
Spin	0
Quadrupole Moment	0
Discovery Year	2017
Parity	+

⁷⁶Fe Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%

History

The first iron used by humans is likely to have come from meteorites. 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. From the Latin word ferrum

Discoverers	Known to the ancients.
Discovery Location
Discovery Year
Etymology (Name Origin)	Anglo-Saxon: iron; symbol from Latin: ferrum (iron).
Pronunciation	EYE-ern (English)

Iron is considered to be non-toxic

The color of blood is due to the hemoglobin, an iron-containing protein

Uses

Iron is used to manufacture steel and other alloys important in construction and manufacturing. Iron is a vital constituent of plant and animal life and works as an oxygen carrier in hemoglobin. Iron oxide mixed with aluminum powder can be ignited to create a thermite reaction, used in welding and purifying ores. Used in steel and other alloys. Essential for humans. It is the chief constituent of hemoglobin which carries oxygen in blood vessels. Its oxides are used in magnetic tapes and disks.

Sources

Obtained from iron ores. Pure metal produced in blast furnaces by layering limestone, coke and iron ore and forcing hot gasses into the bottom. This heats the coke red hot and the iron is reduced from its oxides and liquified where it flows to the bottom

Abundance
Abundance in Earth's crust	56,300 mg/kg
Abundance in Oceans	0.002 mg/L
Abundance in Human Body	0.006 %
Abundance in Meteor	22 %
Abundance in Sun	0.1 %
Abundance in Universe	0.11 %

Nuclear Screening Constants

1	s	0.619
2	p	3.9112
2	s	7.401
3	d	14.8202
3	p	13.2221
3	s	12.3239
4	s	20.566

Iron on ChemicalAid

AEDA subject keyword ID	17568
Art & Architecture Thesaurus ID	300011002
Australian Educational Vocabulary ID	scot/2214
BNCF Thesaurus ID	474
Biblioteca Nacional de España ID	XX524497
Bibliothèque nationale de France ID	11975665r
Brockhaus Enzyklopädie online ID	Hola
Brockhaus Enzyklopädie online ID	eisen-20
CAS Registry Number	7439-89-6
ChEBI ID	18248
ChemSpider ID	22368
CosIng number	83503
DSSTOX compound identifier	DTXCID3023710
DSSTox substance ID	DTXSID5043710
Den Store Danske ID	jern
DrugBank ID	01592
ECHA Substance Infocard ID	100.028.270
Encyclopedie berbere keyword ID	2031
Encyclopædia Britannica Online ID	science/iron-chemical-element
Encyclopædia Universalis ID	fer-l-element-metallique
Encyclopædia Universalis ID	fer-vue-d-ensemble
EuroVoc ID	981
Freebase ID	/m/025rw19
French Vikidia ID	Fer
GND ID	4014002-7
Great Aragonese Encyclopedia ID	6825
Great Russian Encyclopedia Online ID	2625019
Gujarati Vishwakosh entry	આયર્ન-લોહ
HDS ID	026231
HSDB ID	604
Human Metabolome Database ID	HMDB0015531
InChI	InChI=1S/Fe
InChIKey	XEEYBQQBJWHFJM-UHFFFAOYSA-N
Italian Vikidia ID	Ferro
KBpedia ID	Iron
KEGG ID	C00023
Klexikon article ID	Eisen
Library of Congress authority ID	sh85068131
LiverTox ID	Iron
MeSH concept ID	M0011718
MeSH descriptor ID	D007501
NALT ID	33434
NDF-RT ID	N0000146032
NE.se ID	järn
NKCR AUT ID	ph127955
Namuwiki ID	철(원소)
National Diet Library ID	00572915
National Library of Israel J9U ID	987007560416405171
Nomisma ID	fe
OmegaWiki Defined Meaning	2024
Open Food Facts ingredient ID	iron
PACTOLS thesaurus ID	pcrtJWWucnutA0
PSH ID	5775
PubChem CID	23925
Quora topic ID	Iron
RKD thesaurus ID	37450
RxNorm ID	90176
Römpp online ID	RD-05-00418
STW Thesaurus for Economics ID	14281-3
Spanish Cultural Heritage thesauri ID	materias/1000924
Spanish Vikidia ID	Hierro
Store norske leksikon ID	jern
Treccani ID	ferro
UK Archival Thesaurus ID	f2/mt225/4347/3178
UMLS CUI	C0302583
UNESCO Thesaurus ID	concept10788
UNII	E1UOL152H7
UNSPSC Code	11101713
WikiSkripta ID	7294
Wolfram Language entity code	Entity["Mineral", "Iron"]
WordNet 3.1 Synset ID	14666595-n
YSO ID	11738
ZVG number	8210

Iron (Fe)

Properties

Isotopes of Iron

45Fe

45Fe Decay Modes

46Fe

46Fe Decay Modes

47Fe

47Fe Decay Modes

48Fe

48Fe Decay Modes

49Fe

49Fe Decay Modes

50Fe

50Fe Decay Modes

51Fe

51Fe Decay Modes

52Fe

52Fe Decay Modes

53Fe

53Fe Decay Modes

54Fe

54Fe Decay Modes

55Fe

55Fe Decay Modes

56Fe

57Fe

58Fe

59Fe

59Fe Decay Modes

60Fe

60Fe Decay Modes

61Fe

61Fe Decay Modes

62Fe

62Fe Decay Modes

63Fe

63Fe Decay Modes

64Fe

64Fe Decay Modes

65Fe

65Fe Decay Modes

66Fe

66Fe Decay Modes

67Fe

67Fe Decay Modes

68Fe

68Fe Decay Modes

69Fe

69Fe Decay Modes

70Fe

70Fe Decay Modes

71Fe

71Fe Decay Modes

72Fe

72Fe Decay Modes

73Fe

73Fe Decay Modes

74Fe

74Fe Decay Modes

75Fe

75Fe Decay Modes

76Fe

76Fe Decay Modes