Introduction
Group: 6 or VI B
Atomic Weight: 51.9961
Period: 4
CAS Number: 7440-47-3
Classification
No Stable Isotopes
Solid
Liquid
Gas
Solid (Predicted)
Description • Uses/Function
Discovered in 1797 by Vauquelin, who prepared the metal the next year, chromium is a steel-gray, lustrous, hard metal that takes a high polish.The principal ore is chromite (FeCr2O4), which is found in Zimbabwe, Russia, Transvaal, Turkey, Iran, Albania, Finland, Democratic Republic ofMadagascar, and the Philippines. The metal is usually produced by reducing the oxide with aluminum. Chromium is used to harden steel, tomanufacture stainless steel, and to form many useful alloys. Much is used in plating to produce a hard, beautiful surface and to prevent corrosion.Chromium is used to give glass an emerald green color. It finds wide use as a catalyst. All compounds of chromium are colored; the most importantare the chromates of sodium and potassium (K2CrO4) and the dichromates (K2Cr2O7) and the potassium and ammonium chrome alums, as KCr(SO4)2· 12H2O. The dichromates are used as oxidizing agents in quantitative analysis, also in tanning leather. Other compounds are of industrial value; leadchromate is chrome yellow, a valued pigment. Chromium compounds are used in the textile industry as mordants, and by the aircraft and other industriesfor anodizing aluminum. The refractory industry has found chromite useful for forming bricks and shapes, as it has a high melting point, moderatethermal expansion, and stability of crystalline structure. Many chromium compounds are toxic and should be handled with proper safeguards. Naturalchromium contains four isotopes. Sixteen other isotopes are known. Chromium metal (99.99%) costs about $200/kg. Commercial grade chromium(99%) costs about $75/kg. 1
• "Stainless steels show high tensile strength and excellent resistance to corrosion. The most common kind contains 14-18% chromium and 7-9% nickel." 2
• "insulin action…believed to promote the action of insulin and thus influences the metabolism of carbohydrates, fats, and proteins." 3
Physical Properties
Melting Point:4* 1907 °C = 2180.15 K = 3464.6 °F
Electron Configuration: *[Ar] 4s1 3d5
n = 3
Electronegativity (Pauling scale):6 1.66
Specific Heat: 0.449 J/g°C 10 = 23.346 J/mol°C = 0.107 cal/g°C = 5.580 cal/mol°C
4 Cr (s) + 3 O2 (g) → 2 Cr2O3 (s) 16
Earth - Source Compounds: oxides 19
External Links:
(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:9.
Boiling Point:4* 2671 °C = 2944.15 K = 4839.8 °F
Sublimation Point:4
Triple Point:4
Critical Point:4
Density:5 7.15 g/cm3
* - at 1 atm
Electron Configuration
Block: d
Highest Occupied Energy Level: 4
Valence Electrons:
Quantum Numbers:
ℓ = 2
mℓ = 2
ms = +½
Bonding
Electropositivity (Pauling scale): 2.34
Electron Affinity:7 0.666 eV
Oxidation States: +3,2,6
Work Function:8 4.40 eV = 7.0488E-19 J
Ionization Potential
eV 9
kJ/mol
1
6.7665
652.9
2
16.4857
1590.6
3
30.96
2987.2
4
49.16
4743.2
5
69.46
6701.9
6
90.6349
8744.9
7
160.18
15455.0
8
184.7
17820.8
Ionization Potential
eV 9
kJ/mol
9
209.3
20194.4
10
244.4
23581.0
11
270.8
26128.2
12
298
28752.6
13
354.8
34233.0
14
384.168
37066.6
15
1010.6
97508.1
16
1097
105844.4
Ionization Potential
eV 9
kJ/mol
17
1185
114335.1
18
1299
125334.4
19
1396
134693.5
20
1496
144342.0
21
1634
157657.0
22
1721.4
166089.8
23
7481.7
721874.1
24
7894.81
761733.2
Thermochemistry
Thermal Conductivity: 93.7 (W/m)/K, 27°C 11
Heat of Fusion: 16.9 kJ/mol 12 = 325.0 J/g
Heat of Vaporization: 344.3 kJ/mol 13 = 6621.7 J/g
State of Matter
Enthalpy of Formation (ΔHf°)14
Entropy (S°)14
Gibbs Free Energy (ΔGf°)14
(kcal/mol)
(kJ/mol)
(cal/K)
(J/K)
(kcal/mol)
(kJ/mol)
(s)
0
0
5.645
23.61868
0
0
(ℓ)
6.239
26.103976
8.660
36.23344
5.340
22.34256
(g)
95.00
397.48
41.64
174.22176
84.27
352.58568
Isotopes
Nuclide
Mass 15
Half-Life 15
Nuclear Spin 15
Binding Energy
42Cr
42.00643(32)#
14(3) ms [13(+4-2) ms]
0+
314.63 MeV
43Cr
42.99771(24)#
21.6(7) ms
(3/2+)
331.08 MeV
44Cr
43.98555(5)#
54(4) ms [53(+4-3) ms]
0+
350.33 MeV
45Cr
44.97964(54)
50(6) ms
7/2-#
363.99 MeV
46Cr
45.968359(21)
0.26(6) s
0+
382.31 MeV
47Cr
46.962900(15)
500(15) ms
3/2-
395.97 MeV
48Cr
47.954032(8)
21.56(3) h
0+
411.49 MeV
49Cr
48.9513357(26)
42.3(1) min
5/2-
422.36 MeV
50Cr
49.9460442(11)
STABLE
0+
435.09 MeV
51Cr
50.9447674(11)
27.7025(24) d
7/2-
445.02 MeV
52Cr
51.9405075(8)
STABLE
0+
456.82 MeV
53Cr
52.9406494(8)
STABLE
3/2-
464.89 MeV
54Cr
53.9388804(8)
STABLE
0+
474.83 MeV
55Cr
54.9408397(8)
3.497(3) min
3/2-
481.04 MeV
56Cr
55.9406531(20)
5.94(10) min
0+
489.11 MeV
57Cr
56.943613(2)
21.1(10) s
(3/2-)
494.38 MeV
58Cr
57.94435(22)
7.0(3) s
0+
501.52 MeV
59Cr
58.94859(26)
460(50) ms
5/2-#
505.87 MeV
60Cr
59.95008(23)
560(60) ms
0+
512.08 MeV
61Cr
60.95472(27)
261(15) ms
5/2-#
516.42 MeV
62Cr
61.95661(36)
199(9) ms
0+
522.63 MeV
63Cr
62.96186(32)#
129(2) ms
(1/2-)#
526.04 MeV
64Cr
63.96441(43)#
43(1) ms
0+
531.32 MeV
65Cr
64.97016(54)#
27(3) ms
(1/2-)#
533.80 MeV
66Cr
65.97338(64)#
10(6) ms
0+
539.08 MeV
67Cr
66.97955(75)#
10# ms [>300 ns]
1/2-#
541.56 MeV
Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses. 15
Reactions
2 Cr (s) + 3 Cl2 (g) → 2 CrCl3 (s) 16
16 Cr (s) + 1 S8 (s) → 8 Cr2S (s) 17
2 Al (ℓ) + 1 Cr2O3 (s) → Al2O3 (s alpha-corundum) + 2 Cr (ℓ) 18
Abundance
Earth - Seawater: 0.0003 mg/L 20
Earth -
Crust:
102 mg/kg = 0.0102% 20
Earth -
Lithosphere:
0.012% 21
Earth -
Total:
4120 ppm 22
Mercury -
Total:
7180 ppm 22
Venus -
Total:
4060 ppm 22
Chondrites - Total: 6600 (relative to 106 atoms of Si) 23
Human Body - Total: 0.000003% 24
Compounds
chromium(II) carbide
chromium(II) chloride; chromous chloride
chromium(II) fluoride; chromous fluoride
chromium(II) iodide
chromium(II) selenide
chromium(II, III) oxide
chromium(III) bromide
chromium(III) chloride hexahydrate; chromic chloride hexahydrate
chromium(III) chloride; chromic chloride
chromium(III) fluoride
chromium(III) nitrate nonahydrate
chromium(III) nitrate; chromic nitrate
chromium(III) nitride
chromium(III) oxide; chromium sesquioxide
chromium(III) phosphate; chromic phosphate
chromium(III) picolinate
chromium(III) potassium sulfate dodecahydrate; chromic potassium sulfate dodecahydrate (chrome alum)
chromium(III) potassium sulfate; chromic potassium sulfate
chromium(III) sulfate hexahydrate; chromic sulfate hexahydrate
chromium(III) sulfate; chromic sulfate
Safety Information
Material Safety Data Sheet - ACI Alloys, Inc.
For More Information
American Elements
Chemical & Engineering News
Chemical Elements
ChemGlobe
Chemicool
Environmental Chemistry
Sources
(2) - Whitten, Kenneth W., Davis, Raymond E., and Peck, M. Larry. General Chemistry 6th ed.; Saunders College Publishing: Orlando, FL, 2000; p 912.
(3) - Whitten, Kenneth W., Davis, Raymond E., and Peck, M. Larry. General Chemistry 6th ed.; Saunders College Publishing: Orlando, FL, 2000; p 926-7.
(4) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:132.
(5) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 4:39-4:96.
(6) - Dean, John A. Lange's Handbook of Chemistry, 11th ed.; McGraw-Hill Book Company: New York, NY, 1973; p 4:8-4:149.
(7) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 10:147-10:148.
(8) - Speight, James. Lange's Handbook of Chemistry, 16th ed.; McGraw-Hill Professional: Boston, MA, 2004; p 1:132.
(9) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(10) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:133.
(11) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(12) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(13) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(14) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(15) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).
(16) - Kotz, John C. and Treichel, Paul. Chemistry & Chemical Reactivity 4th ed.; Thomson Brooks/Cole: Belmont, CA, 1999; p 173.
(17) - Zumdahl, Steven and Zumdahl, Susan A. Chemistry 9th ed.; Brooks/Cole: Belmont, CA, 2014; p 131.
(18) - Atkins, Jones, and Laverman. Chemical Principles 6th ed.; W.H. Freeman and Company: New York, NY, 2013; p F94.
(19) - Silberberg, Martin S. Chemistry: The Molecular Nature of Matter and Change, 4th ed.; McGraw-Hill Higher Education: Boston, MA, 2006, p 965.
(20) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 14:17.
(21) - Silberberg, Martin S. Chemistry: The Molecular Nature of Matter and Change, 4th ed.; McGraw-Hill Higher Education: Boston, MA, 2006, p 964.
(22) - Morgan, John W. and Anders, Edward, Proc. Natl. Acad. Sci. USA 77, 6973-6977 (1980)
(23) - Brownlow, Arthur. Geochemistry; Prentice-Hall, Inc.: Englewood Cliffs, NJ, 1979, pp 15-16.
(24) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 7:17.