Chromium

Chromium (Cr)

Hard silvery transition element. Used in decorative electroplating. Discovered in 1797 by Vauquelin.
Atomic Number24
Atomic Weight51.9961
Mass Number52
Group6
Period4
Blockd
Protons24 p+
Neutrons28 n0
Electrons24 e-
Chromium crystals and 1cm3 cube.jpg Animated Bohr Model of Cr (Chromium) Enhanced Bohr Model of Cr (Chromium) Bohr Model: Cr (Chromium) Orbital Diagram of Cr (Chromium)

Properties

Atomic Radius
140 pm
Molar Volume
Covalent Radius
122 pm
Metallic Radius
119 pm
Ionic Radius
73 pm
Crystal Radius
87 pm
Van der Waals Radius
206 pm
Density
7.15 g/cm³
Energy
Proton Affinity
791.3 kJ/mol
Electron Affinity
Ionization Energy
6.76651 eV/particle
Heat of Vaporization
342 kJ/mol
Heat of Fusion
Heat of Formation
397.48 kJ/mol
Electrons
Electron Shells2, 8, 13, 1
Valence Electrons6
Electron Configuration[Ar] 3d5 4s1
Oxidation States-4, -2, -1, 0, 1, 2, 3, 4, 5, 6
Electronegativity
1.66
Electrophilicity
1.1319177597467263 eV/particle
Phases
PhaseSolid
Gas Phase
Boiling Point
2,944.15 K
Melting Point
2,180.15 K
Critical Pressure
Critical Temperature
Triple Point
Visual
Color
Silver
Appearancesilvery metallic
Refractive Index
Thermodynamic Properties
Thermal Conductivity
93.9 W/(m K)
Thermal Expansion
0.0000049 1/K
Molar Heat Capacity
23.35 J/(mol K)
Specific Heat Capacity
0.449 J/(g⋅K)
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
TypeConductor
Electrical Conductivity
7.9 MS/m
Electrical Resistivity
0.00000013 m Ω
Superconducting Point
Magnetism
Typeantiferromagnetic
Magnetic Susceptibility (Mass)
0.0000000445 m³/Kg
Magnetic Susceptibility (Molar)
0.000000002314 m³/mol
Magnetic Susceptibility (Volume)
0.0003177
Magnetic Ordering
Curie Point
Neel Point
393 K
Structure
Crystal StructureBody Centered Cubic (BCC)
Lattice Constant
2.88 Å
Lattice Anglesπ/2, π/2, π/2
Mechanical Properties
Hardness
8.5 MPa
Bulk Modulus
160 GPa
Shear Modulus
115 GPa
Young Modulus
279 GPa
Poisson Ratio
0.21
Speed of Sound
5,940 m/s
Classification
CategoryTransition metals, Transition metals
CAS GroupVIA
IUPAC GroupVIB
Glawe Number55
Mendeleev Number51
Pettifor Number57
Geochemical Classfirst series transition metal
Goldschmidt Classlitophile
Other
Gas Basicity
768.4 kJ/mol
Dipole Polarizability
83 ± 12 a₀
C6 Dispersion Coefficient
602 a₀
Allotropes
Neutron Cross Section
3.1
Neutron Mass Absorption
0.0021
Quantum Numbers7S3
Space Group229 (Im_3m)

Isotopes of Chromium

Stable Isotopes4
Unstable Isotopes26
Radioactive Isotopes25

41Cr

Abundance
Relative Atomic Mass
41.021911 ± 0.000429 Da
Mass Number41
G-Factor
Half Life
Spin3/2
Quadrupole Moment
Discovery Year
Parity+

41Cr Decay Modes
Decay ModeIntensity
p (proton emission)%

42Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
42.007579 ± 0.000322 Da
Mass Number42
G-Factor
0
Half Life
13.3 ± 1 ms
Spin0
Quadrupole Moment
0
Discovery Year1996
Parity+

42Cr Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)94.4%
2p (2-proton emission)%

43Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
42.997885 ± 0.000215 Da
Mass Number43
G-Factor
Half Life
21.1 ± 0.3 ms
Spin3/2
Quadrupole Moment
Discovery Year1992
Parity+

43Cr Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)79.3%
2p (2-proton emission)11.6%
3p0.13%
β+α (β+-delayed α emission)%

44Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
43.985591 ± 0.000055 Da
Mass Number44
G-Factor
0
Half Life
42.8 ± 0.6 ms
Spin0
Quadrupole Moment
0
Discovery Year1987
Parity+

44Cr Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)12%

45Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
44.97905 ± 0.000038 Da
Mass Number45
G-Factor
Half Life
60.9 ± 0.4 ms
Spin7/2
Quadrupole Moment
Discovery Year1974
Parity-

45Cr Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+ p (β+-delayed proton emission)34.4%

46Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
45.968360969 ± 0.000012295 Da
Mass Number46
G-Factor
0
Half Life
224.3 ± 1.3 ms
Spin0
Quadrupole Moment
0
Discovery Year1972
Parity+

46Cr Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

47Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
46.962894995 ± 0.000005578 Da
Mass Number47
G-Factor
Half Life
461.6 ± 1.5 ms
Spin3/2
Quadrupole Moment
Discovery Year1972
Parity-

47Cr Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

48Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
47.954029431 ± 0.000007848 Da
Mass Number48
G-Factor
0
Half Life
21.56 ± 0.03 h
Spin0
Quadrupole Moment
0
Discovery Year1952
Parity+

48Cr Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

49Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
48.95133372 ± 0.000002363 Da
Mass Number49
G-Factor
0.1904 ± 0.0012
Half Life
42.3 ± 0.1 m
Spin5/2
Quadrupole Moment
Discovery Year1942
Parity-

49Cr Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

50Cr

Abundance
4.345 ± 0.013
Relative Atomic Mass
49.946042209 ± 0.0000001 Da
Mass Number50
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year1930
Parity+

50Cr Decay Modes
Decay ModeIntensity
+ (double β+ decay)%

51Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
50.944765388 ± 0.000000178 Da
Mass Number51
G-Factor
0.26685714285714 ± 0.0014285714285714
Half Life
27.7015 ± 0.0011 d
Spin7/2
Quadrupole Moment
Discovery Year1940
Parity-

51Cr Decay Modes
Decay ModeIntensity
ϵ (electron capture)100%

52Cr

Abundance
83.789 ± 0.018
Relative Atomic Mass
51.940504714 ± 0.00000012 Da
Mass Number52
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year1923
Parity+

53Cr

Abundance
9.501 ± 0.017
Relative Atomic Mass
52.940646304 ± 0.000000124 Da
Mass Number53
G-Factor
Half Life
Spin3/2
Quadrupole Moment
-0.15 ± 0.05
Discovery Year1930
Parity-

54Cr

Abundance
2.365 ± 0.007
Relative Atomic Mass
53.938877359 ± 0.000000142 Da
Mass Number54
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year1930
Parity+

55Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
54.940836637 ± 0.000000245 Da
Mass Number55
G-Factor
Half Life
3.497 ± 0.003 m
Spin3/2
Quadrupole Moment
Discovery Year1952
Parity-

55Cr Decay Modes
Decay ModeIntensity
β (β decay)100%

56Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
55.940648977 ± 0.00000062 Da
Mass Number56
G-Factor
0
Half Life
5.94 ± 0.1 m
Spin0
Quadrupole Moment
0
Discovery Year1960
Parity+

56Cr Decay Modes
Decay ModeIntensity
β (β decay)100%

57Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
56.943612112 ± 0.000002 Da
Mass Number57
G-Factor
Half Life
21.1 ± 1 s
Spin3/2
Quadrupole Moment
Discovery Year1978
Parity

57Cr Decay Modes
Decay ModeIntensity
β (β decay)100%

58Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
57.944184501 ± 0.0000032 Da
Mass Number58
G-Factor
0
Half Life
7 ± 0.3 s
Spin0
Quadrupole Moment
0
Discovery Year1980
Parity+

58Cr Decay Modes
Decay ModeIntensity
β (β decay)100%

59Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
58.948345426 ± 0.00000072 Da
Mass Number59
G-Factor
Half Life
1,050 ± 90 ms
Spin1/2
Quadrupole Moment
0
Discovery Year1980
Parity-

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

60Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
59.949641656 ± 0.0000012 Da
Mass Number60
G-Factor
0
Half Life
490 ± 10 ms
Spin0
Quadrupole Moment
0
Discovery Year1980
Parity+

60Cr Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%

61Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
60.95437813 ± 0.000002 Da
Mass Number61
G-Factor
Half Life
243 ± 9 ms
Spin5/2
Quadrupole Moment
Discovery Year1985
Parity-

61Cr Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%

62Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
61.95614292 ± 0.0000037 Da
Mass Number62
G-Factor
0
Half Life
206 ± 12 ms
Spin0
Quadrupole Moment
0
Discovery Year1985
Parity+

62Cr Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%

63Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
62.961161 ± 0.000078 Da
Mass Number63
G-Factor
Half Life
129 ± 2 ms
Spin1/2
Quadrupole Moment
0
Discovery Year1992
Parity-

63Cr Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%

64Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
63.963886 ± 0.000322 Da
Mass Number64
G-Factor
0
Half Life
43 ± 1 ms
Spin0
Quadrupole Moment
0
Discovery Year1992
Parity+

64Cr Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%

65Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
64.969608 ± 0.000215 Da
Mass Number65
G-Factor
Half Life
27.5 ± 2.1 ms
Spin1/2
Quadrupole Moment
0
Discovery Year1997
Parity-

65Cr Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

66Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
65.973011 ± 0.000322 Da
Mass Number66
G-Factor
0
Half Life
23.8 ± 1.8 ms
Spin0
Quadrupole Moment
0
Discovery Year1997
Parity+

66Cr Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

67Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
66.979313 ± 0.000429 Da
Mass Number67
G-Factor
Half Life
Spin1/2
Quadrupole Moment
0
Discovery Year1997
Parity-

67Cr Decay Modes
Decay ModeIntensity
β (β decay)%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

68Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
67.983156 ± 0.000537 Da
Mass Number68
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year2009
Parity+

68Cr Decay Modes
Decay ModeIntensity
β (β decay)%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

69Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
68.989662 ± 0.000537 Da
Mass Number69
G-Factor
Half Life
Spin7/2
Quadrupole Moment
Discovery Year2013
Parity+

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

70Cr

AbundanceRadioactive ☢️
Relative Atomic Mass
69.993945 ± 0.000644 Da
Mass Number70
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year2013
Parity+

70Cr Decay Modes
Decay ModeIntensity
β (β decay)%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

History

In 1797, Louis Nicolas Vauquelin received samples of crocoite ore. In 1798, Vauquelin discovered that he could isolate metallic chromium by heating the oxide in a charcoal oven, making him the discoverer of the element. Vauquelin was also able to detect traces of chromium in precious gemstones, such as ruby or emerald. From the Greek word chroma, color

DiscoverersLouis Vauquelin
Discovery LocationFrance
Discovery Year1797
Etymology (Name Origin)Greek: chrôma (color).
PronunciationKROH-mi-em (English)
In larger amounts, chromium can be toxic and carcinogenic
Chromium oxide was used by the Chinese in the Qin dynasty over 2,000 years ago

Uses

Chromium is used to harden steel, manufacture stainless steel, and form many useful alloys. It is mostly used in plating to produce a hard, beautiful surface and to prevent corrosion. The metal is also widely used as a catalyst. Chromium compounds are valued as pigments for their vivid green, yellow, red and orange colors. Used to make stainless steel. It gives the color to rubies and emeralds. Iron-nickel-chromium alloys in various percentages yield an incredible variety of the most important metals in modern technology.

Sources

Chromite [Fe,Mg(CrO4)] is its most important mineral. Produced commercially by heating its ore in the presence of silicon or aluminium.

Abundance
Abundance in Earth's crust
102 mg/kg
Abundance in Oceans
0.0003 mg/L
Abundance in Human Body
0.000003 %
Abundance in Meteor
0.3 %
Abundance in Sun
0.002 %
Abundance in Universe
0.0015 %

Nuclear Screening Constants

1s0.5862
2p3.9248
2s7.0162
3d14.2434
3p12.534
3s11.6322
4s18.8668