Iron

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 Number26
Atomic Weight55.845
Mass Number56
Group8
Period4
Blockd
Protons26 p+
Neutrons30 n0
Electrons26 e-
Iron electrolytic and 1cm3 cube.jpg Animated Bohr Model of Fe (Iron) Enhanced Bohr Model of Fe (Iron) Bohr Model: Fe (Iron) Orbital Diagram of Fe (Iron)

Properties

Atomic Radius
140 pm
Molar Volume
Covalent Radius
116 pm
Metallic Radius
117 pm
Ionic Radius
63 pm
Crystal Radius
77 pm
Van der Waals Radius
204 pm
Density
7.87 g/cm³
Energy
Proton Affinity
754 kJ/mol
Electron Affinity
Ionization Energy
7.9024678 eV/particle
Heat of Vaporization
340 kJ/mol
Heat of Fusion
13.8 kJ/mol
Heat of Formation
415.5 kJ/mol
Electrons
Electron Shells2, 8, 14, 2
Valence Electrons3
Electron Configuration[Ar] 3d6 4s2
Oxidation States-4, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7
Electronegativity
1.83
Electrophilicity
1.045904228706801 eV/particle
Phases
PhaseSolid
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
Appearancelustrous 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
Specific Heat Capacity
0.449 J/(g⋅K)
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
TypeConductor
Electrical Conductivity
10 MS/m
Electrical Resistivity
0.00000009700000000001 m Ω
Superconducting Point
Magnetism
Typeferromagnetic
Magnetic Susceptibility (Mass)
Magnetic Susceptibility (Molar)
Magnetic Susceptibility (Volume)
Magnetic Ordering
Curie Point
1,043 K
Neel Point
Structure
Crystal StructureBody Centered Cubic (BCC)
Lattice Constant
2.87 Å
Lattice Anglesπ/2, π/2, π/2
Mechanical Properties
Hardness
4 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
CategoryTransition metals, Transition metals
CAS GroupVIIIA
IUPAC GroupVIII
Glawe Number71
Mendeleev Number59
Pettifor Number61
Geochemical Classmajor
Goldschmidt Classsiderophile
Other
Gas Basicity
731.1 kJ/mol
Dipole Polarizability
62 ± 4 a₀
C6 Dispersion Coefficient
482 a₀
Allotropes
Neutron Cross Section
2.56
Neutron Mass Absorption
0.0015
Quantum Numbers5D4
Space Group229 (Im_3m)

Isotopes of Iron

Stable Isotopes4
Unstable Isotopes28
Radioactive Isotopes28

45Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
45.015467 ± 0.000304 Da
Mass Number45
G-Factor
Half Life
2.5 ± 0.2 ms
Spin3/2
Quadrupole Moment
Discovery Year1996
Parity+

45Fe Decay Modes
Decay ModeIntensity
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

AbundanceRadioactive ☢️
Relative Atomic Mass
46.001299 ± 0.000322 Da
Mass Number46
G-Factor
0
Half Life
13 ± 2 ms
Spin0
Quadrupole Moment
0
Discovery Year1992
Parity+

46Fe Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)78.7%
2p (2-proton emission)%

47Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
46.992346 ± 0.000537 Da
Mass Number47
G-Factor
Half Life
21.9 ± 0.2 ms
Spin7/2
Quadrupole Moment
Discovery Year1992
Parity-

47Fe Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)88.4%

48Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
47.980667 ± 0.000099 Da
Mass Number48
G-Factor
0
Half Life
45.3 ± 0.6 ms
Spin0
Quadrupole Moment
0
Discovery Year1987
Parity+

48Fe Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)15.3%

49Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
48.973429 ± 0.000026 Da
Mass Number49
G-Factor
Half Life
64.7 ± 0.3 ms
Spin7/2
Quadrupole Moment
Discovery Year1970
Parity-

49Fe Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)56.7%

50Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
49.962988 ± 0.000009 Da
Mass Number50
G-Factor
0
Half Life
152 ± 0.6 ms
Spin0
Quadrupole Moment
0
Discovery Year1977
Parity+

50Fe Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)0%

51Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
50.956855137 ± 0.000001501 Da
Mass Number51
G-Factor
Half Life
305.4 ± 2.3 ms
Spin5/2
Quadrupole Moment
Discovery Year1972
Parity-

51Fe Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

52Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
51.948113364 ± 0.000000192 Da
Mass Number52
G-Factor
0
Half Life
8.275 ± 0.008 h
Spin0
Quadrupole Moment
0
Discovery Year1948
Parity+

52Fe Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

53Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
52.945305629 ± 0.000001792 Da
Mass Number53
G-Factor
-0.18571428571429 ± 0.0028571428571429
Half Life
8.51 ± 0.02 m
Spin7/2
Quadrupole Moment
Discovery Year1938
Parity-

53Fe Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

54Fe

Abundance
5.845 ± 0.105
Relative Atomic Mass
53.939608189 ± 0.000000368 Da
Mass Number54
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year1923
Parity+

54Fe Decay Modes
Decay ModeIntensity
+ (double β+ decay)%

55Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
54.938291158 ± 0.00000033 Da
Mass Number55
G-Factor
Half Life
2.7562 ± 0.0004 y
Spin3/2
Quadrupole Moment
Discovery Year1939
Parity-

55Fe Decay Modes
Decay ModeIntensity
ϵ (electron capture)100%

56Fe

Abundance
91.754 ± 0.106
Relative Atomic Mass
55.934935537 ± 0.000000287 Da
Mass Number56
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year1923
Parity+

57Fe

Abundance
2.119 ± 0.029
Relative Atomic Mass
56.93539195 ± 0.000000287 Da
Mass Number57
G-Factor
Half Life
Spin1/2
Quadrupole Moment
0
Discovery Year1935
Parity-

58Fe

Abundance
0.282 ± 0.012
Relative Atomic Mass
57.933273575 ± 0.000000339 Da
Mass Number58
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year1935
Parity+

59Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
58.934873492 ± 0.000000354 Da
Mass Number59
G-Factor
-0.22386666666667 ± 0.00026666666666667
Half Life
44.5 ± 0.012 d
Spin3/2
Quadrupole Moment
Discovery Year1938
Parity-

59Fe Decay Modes
Decay ModeIntensity
β (β decay)100%

60Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
59.934070249 ± 0.000003656 Da
Mass Number60
G-Factor
0
Half Life
2.62 ± 0.04 My
Spin0
Quadrupole Moment
0
Discovery Year1957
Parity+

60Fe Decay Modes
Decay ModeIntensity
β (β decay)100%

61Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
60.936746241 ± 0.0000028 Da
Mass Number61
G-Factor
Half Life
5.98 ± 0.06 m
Spin3/2
Quadrupole Moment
Discovery Year1957
Parity-

61Fe Decay Modes
Decay ModeIntensity
β (β decay)100%

62Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
61.936791809 ± 0.000003 Da
Mass Number62
G-Factor
0
Half Life
68 ± 2 s
Spin0
Quadrupole Moment
0
Discovery Year1975
Parity+

62Fe Decay Modes
Decay ModeIntensity
β (β decay)100%

63Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
62.940272698 ± 0.000004618 Da
Mass Number63
G-Factor
Half Life
6.1 ± 0.6 s
Spin5/2
Quadrupole Moment
Discovery Year1980
Parity-

63Fe Decay Modes
Decay ModeIntensity
β (β decay)100%

64Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
63.940987761 ± 0.000005386 Da
Mass Number64
G-Factor
0
Half Life
2 ± 0.2 s
Spin0
Quadrupole Moment
0
Discovery Year1980
Parity+

64Fe Decay Modes
Decay ModeIntensity
β (β decay)100%

65Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
64.945015323 ± 0.000005487 Da
Mass Number65
G-Factor
Half Life
805 ± 10 ms
Spin1/2
Quadrupole Moment
0
Discovery Year1980
Parity-

65Fe Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%

66Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
65.946249958 ± 0.0000044 Da
Mass Number66
G-Factor
0
Half Life
467 ± 29 ms
Spin0
Quadrupole Moment
0
Discovery Year1985
Parity+

66Fe Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%

67Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
66.95093 ± 0.0000041 Da
Mass Number67
G-Factor
Half Life
394 ± 9 ms
Spin1/2
Quadrupole Moment
0
Discovery Year1985
Parity-

67Fe Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%

68Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
67.952875 ± 0.000207 Da
Mass Number68
G-Factor
0
Half Life
188 ± 4 ms
Spin0
Quadrupole Moment
0
Discovery Year1985
Parity+

68Fe Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)0%

69Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
68.957918 ± 0.000215 Da
Mass Number69
G-Factor
Half Life
162 ± 7 ms
Spin1/2
Quadrupole Moment
0
Discovery Year1992
Parity-

69Fe Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

70Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
69.960397 ± 0.000322 Da
Mass Number70
G-Factor
0
Half Life
61.4 ± 0.7 ms
Spin0
Quadrupole Moment
0
Discovery Year1997
Parity+

70Fe Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%

71Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
70.965722 ± 0.000429 Da
Mass Number71
G-Factor
Half Life
34.3 ± 2.6 ms
Spin7/2
Quadrupole Moment
Discovery Year1997
Parity+

71Fe Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

72Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
71.968599 ± 0.000537 Da
Mass Number72
G-Factor
0
Half Life
17 ± 1 ms
Spin0
Quadrupole Moment
0
Discovery Year1997
Parity+

72Fe Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

73Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
72.974246 ± 0.000537 Da
Mass Number73
G-Factor
Half Life
12.9 ± 1.6 ms
Spin7/2
Quadrupole Moment
Discovery Year2010
Parity+

73Fe Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

74Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
73.977821 ± 0.000537 Da
Mass Number74
G-Factor
0
Half Life
5 ± 5 ms
Spin0
Quadrupole Moment
0
Discovery Year2010
Parity+

74Fe Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

75Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
74.984219 ± 0.000644 Da
Mass Number75
G-Factor
Half Life
Spin9/2
Quadrupole Moment
Discovery Year2013
Parity+

75Fe Decay Modes
Decay ModeIntensity
β (β decay)%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

76Fe

AbundanceRadioactive ☢️
Relative Atomic Mass
75.988631 ± 0.000644 Da
Mass Number76
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year2017
Parity+

76Fe Decay Modes
Decay ModeIntensity
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

DiscoverersKnown to the ancients.
Discovery Location
Discovery Year
Etymology (Name Origin)Anglo-Saxon: iron; symbol from Latin: ferrum (iron).
PronunciationEYE-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

1s0.619
2p3.9112
2s7.401
3d14.8202
3p13.2221
3s12.3239
4s20.566