| Chromium - Cr
CAS: 7440-47-3 Description: Hard, brittle, gray metal Classification: Transition Metal Date of Discovery: 1797 Discoverer: Louis Vauquelin Name Origin: Greek chrôma (color) |
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Atomic Number: 24
Number of Neutrons: 28 Atomic Mass: 51.9961(6) amu Melting Point: 1907 °C Boiling Point: 2671 °C Density (293 K): 7.18 to 7.20 g/cm3 Atomic volume: 7.23 cm3/mol Electrical resistivity: 0.0774 10-6/cm 
Thermal conductivity: 0.937 W/cmK Enthalpy of atomization: 397.48 kJ/mol Enthalpy of vaporization: 344.30 kJ/mol Enthalpy of fusion: 16.90 kJ/mol Specific heat capacity: 0.45 J/gK |
Energy levels: 2-8-12-2
Electron configuration: [Ar]3d54s1 Crystal Structure: Cubic body centered Atomic radius: 1.85 Å Covalent radius: 1.18 Å Oxidation States: +2, +3, +6 Electronegativity, Pauling: 1.66 Electron affinity: 0.666 eV First ionization energy: 6.766 eV 2nd ionization energy: 16.50 eV 3rd ionization energy: 30.96 eV Polarizability: 11.6 10-24cm3 |
| Isotope | Natural Abundance | Atomic Mass | Half-life | Decay Mode | Spin |
| 43Cr | 42.9977 | 21 ms | |||
| 44Cr | 43.9855 | 53 ms |  -, (p) |
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| 45Cr | 44.9792 | 0.05 s | +, p |
7/2- | |
| 46Cr | 45.96836 | 0.3 s | + |
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| 47Cr | 46.96291 | 0.51 s | + |
3/2- | |
| 48Cr | 47.95404 | 21.6 h | EC | ||
| 49Cr | 48.951341 | 42.3 m | +, EC |
5/2- | |
| 50Cr | 4.345(13) | 49.94650 | Stable | 0+ | |
| 51Cr | 50.944772 | 27.70 | EC | 7/2- | |
| 52Cr | 83.789(18) | 51.940512 | Stable | - |
0+ |
| 53Cr | 9.501(17) | 52.940653 | Stable | 3/2- | |
| 54Cr | 2.365(7) | 53.938885 | Stable | 0+ | |
| 55Cr | 54.940844 | 3.497 m | - |
3/2- | |
| 56Cr | 55.94065 | 5.9 m | - |
0+ | |
| 57Cr | 56.9438 | 21 s | - |
3/2- | |
| 58Cr | 57.9443 | 7.0 s | - |
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| 59Cr | 58.9487 | 1.0 s | - |
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| 60Cr | 59.9497 | 0.6 s | - |
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| 61Cr | 60.9541 | - |
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| 62Cr | 61.9558 | - |
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| 63Cr | |||||
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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 of Madagascar, and the Phillippines. The metal is usually produced by reducing the oxide with aluminum. Chromium is used to harden steel, to manufacture 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 important are the chromates of sodium and potassium (K2CrO4)and the dichromates (K2Cr2O7) and the potassium and ammonium chrome alums, as KCr(SO4)2·12H20. The dichromates
are used as oxidizing agents in quantitative analysis, also in tanning leather. Other compounds are of industrial value; lead chromate is chrome yellow, a valued pigment. Chromium compounds are used in the textile industry as mordants, and by the aircraft and other industries for anodizing aluminum. The refractory industry has found chromite uaseful for forming bricks and shapes, as it has a high melting point, moderate thermal
expansion, and stability of crystalline structure. Chromium compounds are toxic and should be handled with proper safeguards. Sixteen isotopes are known.
LINKS: Chromium Information Bureau Chromium and water quality Chromium Nitride (CrN) - Chromium Plating Chromium Picolinate Cancer Risk International Chromium Development Association Return
Sources for the information on this website include: Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998. |
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