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| Atomic symbol: Cr |
| Atomic number: 24 |
| Atomic weight: 51.996 |
| Atomic volume: 7.23 cm3/mol |
| Density: 7.19 g/cm3 |
| Period Number: 4 |
| Group number: 6 |
| Group name: Trans. Met. |
| Element classification: Metal |
| Phase at room temperature: Solid |
| Melting Point: 2130.2 K |
| Boiling point: 2963 K |
| Heat of fusion: 16.90 kJ/mol |
| Heat of vaporization: 344.30 kJ/mol |
| Ionization Energy: 6.767 eV |
| 1st ionization energy: 652.8 kJ/mole |
| 2nd ionization energy: 1592 kJ/mole |
| 3rd ionization energy: 2987.2 kJ/mole |
| Electronegativity: 1.66 |
| Electron affinity: 64.3 kJ/mole |
| Specific heat: 0.45 J/gK |
| Heat atomization: 397 kJ/mole atoms |
| Shells: 2,8,13,1 |
| Electron Shell Configuration: [Ar] 3d5 4s1 |
| Minimum oxidation number: -2 |
| Maximum oxidation number: 6 |
| Minimum common oxidation number: 0 |
| Maximum common oxidation no: 6 |
Appearance & Characteristics |
| Structure:: bcc: body-centered cubic |
| Color: silvery-white |
| Hardness: 9 mohs |
| Toxicity: ? |
| Characteristics: hard |
| Uses: CrO2 tape, paint, steel |
| Reaction with air: none |
| Reaction with 6M HCl: mild, =>H2, CrCl3 |
| Reaction with 15M HNO3: passivated |
| Reaction with 6M NaOH: ? |
| Number of isotopes: 4 |
| Oxide(s): Cr2O3 CrO2 CrO3+non-stoich |
| Hydride(s): CrH |
| Chloride(s): CrCl2 CrCl3 |
| Atomic Radius: 128 pm |
| Ionic radius (1- ion): pm |
| Ionic radius (1+ ion): pm |
| Ionic radius (2- ion): pm |
| Ionic radius (2+ ion): 90.5 pm |
| Ionic radius (3+ ion): 75.5 pm |
| Thermal conductivity: 93.9 J/m-sec-deg |
| Electrical conductivity: 77.519 1/mohm-cm |
| Polarizability: 11.6 A^3 |
| Source: Chromite (oxide) |
| Relative abundance solar system: 4.130 log |
| Abundance earth's crust: 2 log |
| Estimated crustal abundance: 1.02×102 milligrams per kilogram |
| Estimated oceanic abundance: 3×10-4 milligrams per liter |
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| (Gr. chroma: color) Discovered in 1797 by Vauquelin, who prepared the metal in the following year, chromium is a steel-gray, lustrous, hard metal that takes a high polish. |
| 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. |
All compounds of chromium are colored. The most important chromates are those of sodium and potassium, the dichromates, and the potassium and ammonium chrome alums. 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.
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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. Chromium gives glass an emerald green color and is widely used as a catalyst.
The refractory industry uses chromite for forming bricks and shapes, as it has a high melting point, moderate thermal expansion, and stability of crystalline structure.
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