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Atomic symbol: Ce |
Atomic number: 58 |
Atomic weight: 140.12 |
Atomic volume: 20.67 cm3/mol |
Density: 6.78 g/cm3 |
Period Number: 6 |
Group number: none |
Group name: Rare Earth, Lanthanide series |
Element classification: Metal |
Phase at room temperature: Solid |
Melting Point: 1071.2 K |
Boiling point: 3743 K |
Heat of fusion: 5.460 kJ/mol |
Heat of vaporization: 414.0 kJ/mol |
Ionization Energy: 5.539 eV |
1st ionization energy: 527.4 kJ/mole |
2nd ionization energy: 1047 kJ/mole |
3rd ionization energy: 1949 kJ/mole |
Electronegativity: 1.12 |
Electron affinity: 50 kJ/mole |
Specific heat: 0.19 J/gK |
Heat atomization: 419 kJ/mole atoms |
Shells: 2,8,18,20,8,2 |
Electron Shell Configuration: [Xe] 4f2 6s2 |
Minimum oxidation number: 0 |
Maximum oxidation number: 4 |
Minimum common oxidation number: 0 |
Maximum common oxidation no: 4 |
Appearance & Characteristics |
Structure:: fcc: face-centered cubic |
Color: silvery-white |
Hardness: mohs |
Toxicity: ? |
Characteristics: malleable |
Uses: self-cleaning ovens(CeO2) |
Reaction with air: vigorous, w/ht =>CeO2 |
Reaction with 6M HCl: vigorous, =>H2, CeCl3 |
Reaction with 15M HNO3: mild, =>Ce(NO3)3 |
Reaction with 6M NaOH: ? |
Number of isotopes: 4 |
Oxide(s): Ce2O3 CeO2 |
Hydride(s): CeH2 CeH3 |
Chloride(s): CeCl3 |
Atomic Radius: 182 pm |
Ionic radius (1- ion): pm |
Ionic radius (1+ ion): pm |
Ionic radius (2- ion): pm |
Ionic radius (2+ ion): pm |
Ionic radius (3+ ion): 115 pm |
Thermal conductivity: 11.3 J/m-sec-deg |
Electrical conductivity: 13.333 1/mohm-cm |
Polarizability: 29.6 A^3 |
Source: Monazite(phosphate),bastnaesite |
Relative abundance solar system: 0.055 log |
Abundance earth's crust: 1.8 log |
Estimated crustal abundance: 6.65×101 milligrams per kilogram |
Estimated oceanic abundance: 1.2×10-6 milligrams per liter |
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Cerium was named for the asteroid Ceres, which was discovered in 1801. The element was discovered two years later in 1803 by Klaproth and by Berzelius and Hisinger. In 1875 Hillebrand and Norton prepared the metal. |
Cerium is the most abundant so-called rare-earth metals. It is found in a number of minerals including allanite (also known as orthite), monazite, bastnasite, cerite, and samarskite. Monazite and bastnasite are presently the more important sources of cerium.
Large deposits of monazite (found on the beaches of Travancore, India and in river sands in Brazil), allanite (in the western United States), and bastnasite (in Southern California) will supply cerium, thorium, and the other rare-earth metals for many years to come.
Metallic cerium is prepared by metallothermic reduction techniques, such as reducing cerous fluoride with calcium, or using electrolysis of molten cerous chloride or others processes. The metallothermic technique produces high-purity cerium.
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Cerium is especially interesting because of its variable electronic structure. The energy of the inner 4f level is nearly the same as that of the outer (valence) electrons, and only small amounts of energy are required to change the relative occupancy of these electronic levels. This gives rise to dual valency states.
For example, a volume change of about 10 percent occurs when cerium is subjected to high pressures or low temperatures. Cesium's valence appears to change from about 3 to 4 when it is cooled or compressed. The low temperature behavior of cerium is complex.
Cerium is an iron-gray lustrous metal. It is malleable, and oxidizes very readily at room temperature, especially in moist air. Except for europium, cerium is the most reactive of the rare-earth metals. It decomposes slowly in cold water and rapidly in hot water.
Alkali solutions and dilute and concentrated acids attack the metal rapidly. The pure metal is likely to ignite if scratched with a knife.
Ceric slats are orange red or yellowish; cerous salts are usually white.
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Cerium is a component of misch metal, which is extensively used in the manufacture of pyrophoric alloys for cigarette lighters. While cerium is not radioactive, the impure commercial grade may contain traces of thorium, which is radioactive. The oxide is an important constituent of incandescent gas mantles and is emerging as a hydrocarbon catalyst in self cleaning ovens where it can be incorporated into oven walls to prevent the collection of cooking residues.
As ceric sulfate is used extensively as a volumetric oxidizing agent in quantitative analysis. Cerium compounds are used in the manufacture of glass, both as a component and as a decolorizer.
The oxide is finding increased use as a glass polishing agent instead of rouge, for it polishes much faster than rouge. Cerium, with other rare earths, is used in carbon-arc lighting, especially in the motion picture industry. It is also useful as a catalyst in petroleum refining and in metallurgical and nuclear applications.
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