Cr 24

Chromium (Cr)

transition-metal

Period: 4 Group: 6 Block: s

Solid

Standard Atomic Weight

Electron configuration

[Ar] 3d⁵ 4s¹

Melting point

1906.85 °C (2180 K)

Boiling point

2670.85 °C (2944 K)

Density

7150 kg/m³

Oxidation states

−4, −2, −1, 0, +1, +2, +3, +4, +5, +6

Electronegativity (Pauling)

1.66

Ionization energy (1st)

Discovery year

1797

Atomic radius

140 pm

Details

Name origin Greek: chrôma (color).

Discovery country France

Discoverers Louis Vauquelin

Chromium is a hard transition metal best known for forming adherent, protective oxide films and for giving many minerals and compounds strong colors. It occurs mainly in chromite ores and is an important alloying element in stainless and heat-resisting steels. Its chemistry spans several oxidation states, especially +3 and +6, with a sharp contrast between relatively stable Cr(III) compounds and strongly oxidizing, often toxic Cr(VI) species.

Chromium is used extensively in automobile trim as chromium metal because of its shiny finish and corrosion resistance.

The name derives from the Greek chroma for "colour", from the many coloured compounds of chromium. It was discovered in 1797 by the French chemist and pharmacist Nicolas-Louis Vauquelin, who also isolated chromium in 1798.

Chromium was discovered by Louis-Nicholas Vauquelin while experimenting with a material known as Siberian red lead, also known as the mineral crocoite (PbCrO4), in 1797. He produced chromium oxide (CrO3) by mixing crocoite with hydrochloric acid (HCl). Although he believed a method for isolating chromium didn't yet exist, Vauquelin was pleasantly surprised in 1798 to discover that he was able to obtain metallic chromium by simply heating chromium oxide in a charcoal oven. Today, chromium is primarily obtained by heating the mineral chromite (FeCr2O4) in the presence of aluminum or silicon.

From the Greek word chroma, color. Chromium is a steel-gray, lustrous, hard metal that takes a high polish. Discovered in 1797 by the Frenchman Louis Nicolas Vauquelin.

Read about Chromium on Wikipedia

Images

Properties

Physical

Atomic radius (empirical) 140 pm

Covalent radius 139 pm

Van der Waals radius 189 pm

Metallic radius 119 pm

Density

Molar volume 0.00723 L/mol

Phase at STP solid

Melting point 1906.85 °C

Boiling point 2670.85 °C

Thermal conductivity 93.9 W/(m·K)

Specific heat capacity 0.449 J/(g·K)

Molar heat capacity 23.35 J/(mol·K)

Crystal structure bcc

Chemical

Electronegativity (Pauling) 1.66

Electronegativity (Allen) 1.65

Electron affinity

Ionization energy (1st)

Ionization energy (2nd)

Ionization energy (3rd)

Ionization energy (4th)

Ionization energy (5th)

Oxidation states −4, −2, −1, 0, +1, +2, +3, +4, +5, +6

Valence electrons 6

Electron configuration

Electron configuration (semantic)

Thermodynamic

Heat of fusion 0.21246826 eV

Heat of vaporization 3.518682 eV

Heat of sublimation 4.119811 eV

Heat of atomization 4.119811 eV

Atomization enthalpy

Nuclear

Stable isotopes 3

Discovery year 1797

Abundance

Abundance (Earth's crust) 102 mg/kg

Abundance (ocean)

Reactivity

N/A

Crystal Structure

Lattice constant a 288 pm

Electronic Structure

Electrons per shell 2, 8, 13, 1

Identifiers

CAS number 7440-47-3

Term symbol

InChI InChI=1S/Cr

InChI Key VYZAMTAEIAYCRO-UHFFFAOYSA-N

Electron Configuration Measured

Ion charge

Protons 24

Electrons 24

Charge Neutral

Configuration Cr: 3d⁵ 4s¹

[Ar] 3d⁵ 4s¹

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹

Orbital diagram

↑↓

2/2

↑↓

2/2

↑↓

6/6

↑↓

2/2

↑↓

6/6

↑

1/2 1↑

↑

5/10 5↑

Total electrons: 24 Unpaired: 6

Atomic model

Protons 24

Neutrons 28

Electrons 24

Mass number 52

Stability Stable

Isotopes change neutron count, mass, and stability — not the electron configuration of a neutral atom.

Schematic atomic model, not to scale.

Atomic Fingerprint

Emission / Absorption Spectrum

Emission Visible: 380–750 nm

Isotope Distribution

Mass number	Atomic mass (u)	Natural abundance	Half-life
52 Stable	51.94050623 ± 0.00000063	83.7890%	Stable
53 Stable	52.94064815 ± 0.00000062	9.5010%	Stable
54 Stable	53.93887916 ± 0.00000061	2.3650%	Stable

Measured

Phase / State

Solid 25 °C (298.15 K)

Reason: 1881.8 °C below melting point (1906.85 °C)

Melting point 1906.85 °C

Boiling point 2670.85 °C

Below melting by 1881.8 °C

0 K Current temperature: 25 °C 6000 K

Phase timeline

Schematic, not to scale

Solid

Liquid

Gas

Melting

Boiling

25°C

Solid

Liquid

Gas

Current

Phase transition points

Melting point Literature

1906.85 °C

Boiling point Literature

2670.85 °C

Current phase Calculated
Solid

Transition energies

Heat of fusion Literature

0.21246826 eV

Energy required to melt 1 mol at melting point

Heat of vaporization Literature

3.518682 eV

Energy required to vaporize 1 mol at boiling point

Heat of sublimation Literature

4.119811 eV

Energy required to sublime 1 mol at sublimation point

Density

Reference density Literature

7150 kg/m³

At standard conditions

Current density Calculated

7150 kg/m³

At standard conditions

Atomic Spectra

Showing 10 of 24 Atomic Spectra. Sorted by ion charge (ascending).

Lines Holdings ?

Ion	Charge	Total lines	Transition probabilities	Level designations
Cr I	0	4369	527	4369
Cr II	+1	5370	92	5370
Cr III	+2	136	0	0
Cr IV	+3	188	102	102
Cr V	+4	193	104	193
Cr VI	+5	102	26	102
Cr VII	+6	143	4	143
Cr VIII	+7	36	9	36
Cr IX	+8	58	18	58
Cr X	+9	75	46	75

NIST Lines Holdings →

Levels Holdings ?

Ion	Charge	Levels
Cr I	0	659
Cr II	+1	914
Cr III	+2	215
Cr IV	+3	155
Cr V	+4	47
Cr VI	+5	63
Cr VII	+6	66
Cr VIII	+7	34
Cr IX	+8	49
Cr X	+9	39

NIST Levels Holdings →

24 Cr 51.9961

Chromium — Atomic Orbital Visualizer

[Ar]3d54s1

Energy levels 2 8 13 1

Oxidation states -4, -2, -1, 0, +1, +2, +3, +4, +5, +6

HOMO 4s n=4 · l=0 · m=0

Chromium — Atomic Orbital Visualizer Preview

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24 Cr 51.9961

Chromium — Crystal Structure Visualizer

Body-Centered Cubic · Pearson cI2

Experimental

Pearson cI2

Coord. № 8

Packing 68.000%

Chromium — Crystal Structure Visualizer Preview

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Ionic Radii

Charge	Coordination	Spin	Radius
+2	6	low	73 pm
+2	6	high	80 pm
+3	6	N/A	61.5 pm
+4	4	N/A	41 pm
+4	6	N/A	55.00000000000001 pm
+5	4	N/A	34.5 pm
+5	6	N/A	49 pm
+5	8	N/A	56.99999999999999 pm
+6	4	N/A	26 pm
+6	6	N/A	44 pm

Compounds

51.996 u

Cr+3

51.996 u

Cr+6

51.996 u

50.945 u

Cr+2

51.996 u

Cr+5

51.996 u

Cr+4

51.996 u

49.946 u

52.941 u

Cr+6

50.945 u

Cr+3

50.945 u

48.951 u

47.954 u

53.939 u

51.941 u

Cr+3

49.946 u

Cr+6

52.941 u

Isotopes (3)

Mass number	Atomic mass (u)	Natural abundance	Half-life	Decay mode
52 Stable	51.94050623 ± 0.00000063	83.7890% ± 0.0180%	Stable	stable
53 Stable	52.94064815 ± 0.00000062	9.5010% ± 0.0170%	Stable	stable
54 Stable	53.93887916 ± 0.00000061	2.3650% ± 0.0070%	Stable	stable

52 Stable

Atomic mass (u) 51.94050623 ± 0.00000063

Natural abundance 83.7890% ± 0.0180%

Half-life Stable

Decay mode

stable

53 Stable

Atomic mass (u) 52.94064815 ± 0.00000062

Natural abundance 9.5010% ± 0.0170%

Half-life Stable

Decay mode

stable

54 Stable

Atomic mass (u) 53.93887916 ± 0.00000061

Natural abundance 2.3650% ± 0.0070%

Half-life Stable

Decay mode

stable

Spectral Lines

Showing 50 of 2531 Spectral Lines. Only spectral lines with measured intensity are shown by default.

Wavelength (nm)	Intensity	Ion stage	Type	Transition	Accuracy	Source
540.978408 nm	8500	Cr I	emission	3d4.4s2 a 5D → 3d5.(6S).4p z 5P*	Measured	NIST
534.57965 nm	5100	Cr I	emission	3d4.4s2 a 5D → 3d5.(6S).4p z 5P*	Measured	NIST
529.827202 nm	3540	Cr I	emission	3d4.4s2 a 5D → 3d5.(6S).4p z 5P*	Measured	NIST
435.17622 nm	3500	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5F	Measured	NIST
534.83147 nm	3200	Cr I	emission	3d4.4s2 a 5D → 3d5.(6S).4p z 5P*	Measured	NIST
434.450128 nm	3100	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5F	Measured	NIST
433.944609 nm	2600	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5F	Measured	NIST
526.415341 nm	2600	Cr I	emission	3d4.4s2 a 5D → 3d5.(6S).4p z 5P*	Measured	NIST
464.616212 nm	2400	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) y 5P	Measured	NIST
529.669109 nm	2100	Cr I	emission	3d4.4s2 a 5D → 3d5.(6S).4p z 5P*	Measured	NIST
391.915844 nm	2030	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5D	Measured	NIST
433.755701 nm	1900	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5F	Measured	NIST
740.01798 nm	1900	Cr I	emission	3d5.(6S).4p z 7P* → 3d5.(6S).5s e 7S	Measured	NIST
465.215743 nm	1750	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) y 5P	Measured	NIST
435.962444 nm	1420	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5F	Measured	NIST
437.127465 nm	1400	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5F	Measured	NIST
735.58903 nm	1400	Cr I	emission	3d5.(6S).4p z 7P* → 3d5.(6S).5s e 7S	Measured	NIST
461.612404 nm	1360	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) y 5P	Measured	NIST
390.875593 nm	1310	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5D	Measured	NIST
449.685195 nm	1300	Cr I	emission	3d5.(6S).4s a 5S → 3d4.(5D).4s.4p.(3P) y 5P	Measured	NIST
524.756509 nm	1250	Cr I	emission	3d4.4s2 a 5D → 3d5.(6S).4p z 5P*	Measured	NIST
460.074835 nm	1190	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) y 5P	Measured	NIST
433.971051 nm	1120	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5F	Measured	NIST
462.617342 nm	1100	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) y 5P	Measured	NIST
435.104951 nm	1080	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5F	Measured	NIST
438.4975 nm	1060	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5F	Measured	NIST
526.571497 nm	1050	Cr I	emission	3d4.4s2 a 5D → 3d5.(6S).4p z 5P*	Measured	NIST
452.64538 nm	960	Cr I	emission	3d5.(4G).4s a 5G → 3d5.(4G).4p z 5G*	Measured	NIST
454.595302 nm	930	Cr I	emission	3d5.(6S).4s a 5S → 3d4.(5D).4s.4p.(3P) y 5P	Measured	NIST
532.832346 nm	930	Cr I	emission	3d5.(6S).4p z 7P* → 3d5.(6S).4d e 7D	Measured	NIST
388.32867 nm	910	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5D	Measured	NIST
392.86372 nm	880	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5D	Measured	NIST
388.521354 nm	810	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5D	Measured	NIST
746.23079 nm	800	Cr I	emission	3d5.(6S).4p z 7P* → 3d5.(6S).5s e 7S	Measured	NIST
453.073802 nm	770	Cr I	emission	3d5.(4G).4s a 5G → 3d5.(4G).4p z 5G*	Measured	NIST
388.679508 nm	740	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5D	Measured	NIST
392.102067 nm	740	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5D	Measured	NIST
394.148757 nm	720	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5D	Measured	NIST
697.83983 nm	640	Cr I	emission	3d4.(5D).4s.4p.(3P) y 7P → 3d5.(6S).4d e 7D	Measured	NIST
396.3684 nm	620	Cr I	emission	3d5.(4G).4s a 5G → 3d5.(4G).4p y 5H*	Measured	NIST
453.569676 nm	600	Cr I	emission	3d5.(4G).4s a 5G → 3d5.(4G).4p z 5G*	Measured	NIST
390.290908 nm	590	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) z 5D	Measured	NIST
455.864413 nm	590	Cr II	emission	3d5 b 4F → 3d4.(5D).4p z 4D*	Measured	NIST
461.335727 nm	590	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) y 5P	Measured	NIST
396.974253 nm	570	Cr I	emission	3d5.(4G).4s a 5G → 3d5.(4G).4p y 5H*	Measured	NIST
458.004789 nm	560	Cr I	emission	3d5.(6S).4s a 5S → 3d4.(5D).4s.4p.(3P) y 5P	Measured	NIST
530.074563 nm	530	Cr I	emission	3d4.4s2 a 5D → 3d5.(6S).4p z 5P*	Measured	NIST
397.665859 nm	520	Cr I	emission	3d5.(4G).4s a 5G → 3d5.(4G).4p y 5H*	Measured	NIST
454.04987 nm	500	Cr I	emission	3d5.(4G).4s a 5G → 3d5.(4G).4p z 5G*	Measured	NIST
459.139098 nm	490	Cr I	emission	3d4.4s2 a 5D → 3d4.(5D).4s.4p.(3P) y 5P	Measured	NIST

Extended Properties

Covalent Radii (Extended)

Covalent radius (Pyykkö)

Covalent radius (Pyykkö, double)

Covalent radius (Pyykkö, triple)

Covalent radius (Bragg)

Van der Waals Radii

Batsanov

Alvarez

UFF

MM3

Atomic & Metallic Radii

Atomic radius (Rahm)

Metallic radius (C12)

Numbering Scales

Mendeleev

Pettifor

Glawe

Electronegativity Scales

Ghosh

Miedema

Gunnarsson–Lundqvist

Robles–Bartolotti

Polarizability & Dispersion

Dipole polarizability

Dipole polarizability (unc.)

C₆

C₆ (Gould–Bučko)

Chemical Affinity

Proton affinity

Gas basicity

Miedema Parameters

Miedema molar volume

Miedema electron density

Supply Risk & Economics

Production concentration

Relative supply risk

Reserve distribution

Political stability (top producer)

Political stability (top reserve)

Phase Transitions & Allotropes

Melting point	2180.15 K
Boiling point	2944.15 K

Oxidation State Categories

0 extended

+6 main

−2 extended

−4 extended

+4 extended

+1 extended

+5 extended

−1 extended

+3 main

+2 extended

Advanced Reference Data

Screening Constants (7)

n	Orbital	σ
1	s	0.5862
2	p	3.9248
2	s	7.0162
3	d	14.2434
3	p	12.534
3	s	11.6322
4	s	18.8668

Crystal Radii Detail (10)

Charge	CN	Spin	r_crystal (pm)	Origin
2	VI	LS	87	estimated,
2	VI	HS	94	from r^3 vs V plots,
3	VI		75.5	from r^3 vs V plots,
4	IV		55
4	VI		69	from r^3 vs V plots,
5	IV		48.5	from r^3 vs V plots,
5	VI		63	estimated, from r^3 vs V plots,
5	VIII		71
6	IV		40
6	VI		58	calculated,

Isotope Decay Modes (52)

Isotope	Mode	Intensity
41	p	—
42	B+	100%
42	B+p	94.4%
42	2p	—
43	B+	100%
43	B+p	79.3%
43	2p	11.6%
43	3p	0.1%
43	B+A	—
44	B+	100%

X‑ray Scattering Factors (751)

Energy (eV)	f₁	f₂
0.42	-0.0076	0.02756
0.46	-0.01	0.03022
0.5	-0.0123	0.03301
0.54	-0.0148	0.03586
0.58	-0.0176	0.03897
0.62	-0.0202	0.04225
0.66	-0.0225	0.04515
0.7	-0.0257	0.04771
0.74	-0.0292	0.05056
0.78	-0.0332	0.05331

Additional Data

Estimated Crustal Abundance

The estimated element abundance in the earth's crust.

1.02×102 milligrams per kilogram

References (1)

[5] Chromium https://education.jlab.org/itselemental/ele024.html

Estimated Oceanic Abundance

The estimated element abundance in the earth's oceans.

3×10-4 milligrams per liter

References (1)

[5] Chromium https://education.jlab.org/itselemental/ele024.html

Sources

Sources of this element.

The principal ore is chromite, which is found in Zimbabwe, Russia, New Zealand, Turkey, Iran, Albania, Finland, Democratic Republic of Madagascar, and the Phillippines. The metal is usually produced by reducing the oxide with aluminum.

References (1)

[6] Chromium https://periodic.lanl.gov/24.shtml

References

(9)

1 PubChem

Data deposited in or computed by PubChem

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2 Atomic Mass Data Center (AMDC), International Atomic Energy Agency (IAEA)

The half-life and atomic mass data was provided by the Atomic Mass Data Center at the International Atomic Energy Agency.

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3 IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW)

Chromium

Element data are cited from the Atomic weights of the elements (an IUPAC Technical Report). The IUPAC periodic table of elements can be found at https://iupac.org/what-we-do/periodic-table-of-elements/. Additional information can be found within IUPAC publication doi:10.1515/pac-2015-0703 Copyright © 2020 International Union of Pure and Applied Chemistry.

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4 IUPAC Periodic Table of the Elements and Isotopes (IPTEI)

The information are cited from Pure Appl. Chem. 2018; 90(12): 1833-2092, https://doi.org/10.1515/pac-2015-0703.

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License note: Copyright (c) 2020 International Union of Pure and Applied Chemistry. The International Union of Pure and Applied Chemistry (IUPAC) contribution within Pubchem is provided under a CC-BY-NC-ND 4.0 license, unless otherwise stated.

5 Jefferson Lab, U.S. Department of Energy

Chromium

Thomas Jefferson National Accelerator Facility (Jefferson Lab) is one of 17 national laboratories funded by the U.S. Department of Energy. The lab's primary mission is to conduct basic research of the atom's nucleus using the lab's unique particle accelerator, known as the Continuous Electron Beam Accelerator Facility (CEBAF). For more information visit https://www.jlab.org/

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License note: Please see citation and linking information: https://education.jlab.org/faq/index.html

6 Los Alamos National Laboratory, U.S. Department of Energy

Chromium

The periodic table at the LANL (Los Alamos National Laboratory) contains basic element information together with the history, source, properties, use, handling and more. The provenance data may be found from the link under the source name.

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7 NIST Physical Measurement Laboratory

Chromium

The periodic table contains NIST's critically-evaluated data on atomic properties of the elements. The provenance data that include data for atomic spectroscopy, X-ray and gamma ray, radiation dosimetry, nuclear physics, and condensed matter physics may be found from the link under the source name. Ref: https://www.nist.gov/pml/atomic-spectra-database

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8 PubChem Elements

Chromium

This section provides all form of data related to element Chromium.

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9 PubChem Elements

Chromium

The element property data was retrieved from publications.

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Last updated: May 1, 2026

Data verified: May 12, 2026

Content is reviewed against latest scientific data.