CHROMIUM

Introduction

Atomic Number: 24
Group: 6 or VI B
Atomic Weight: 51.9961
Period: 4
CAS Number: 7440-47-3

Classification

Chalcogen
Halogen
Noble Gas
Lanthanoid
Actinoid
Rare Earth Element
Platinum Group Metal
Transuranium
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
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

Electron Configuration:  *[Ar] 4s1 3d5
Block: d
Highest Occupied Energy Level: 4
Valence Electrons: 

Quantum Numbers:

n = 3
ℓ = 2
m = 2
ms = +½

Bonding

Electronegativity (Pauling scale):6 1.66
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

Specific Heat: 0.449 J/g°C 10 = 23.346 J/mol°C = 0.107 cal/g°C = 5.580 cal/mol°C
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

Abundance

Earth - Source Compounds: oxides 19
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

Safety Information


Material Safety Data Sheet - ACI Alloys, Inc.

For More Information

External Links:

Sources

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:9.
(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.