Cerium, Heaven, This, 58

Aeneral

Heaven [t͡seːr] (or even destruction. Cerium called) is a chemical element with the element symbol Ce and atomic number 58. In the periodic table it is in the group of lanthanides and is thus also to the metals of the rare Erden.Cer was 1803 by Jacob Berzelius and Wilhelm Jöns appointed by Hisinger and simultaneously discovered by Martin Heinrich Klaproth, and after the dwarf planet Ceres. The representation of the element succeeded Carl Gustav Mosander 1825 by reducing the chloride with cerium Natrium.In nature is associated with other lanthanides from cerium earths in so-called, such as in allanite (As, This, The, And)²(To the, Faith)³(SiO4)³(OH), in monazite (This,

The, Th, Nd, And)PO4 and in bastnaesite (This, The, And)CO ³ F.

Extraction

After an extensive separation of the cerium oxide, the companion with hydrogen fluoride to cerium fluoride implemented. It is then reduced with calcium to form calcium fluoride to cerium. The removal of residual calcium residues and contaminants carried in an additional remelting in vacuum.

Special features

The silvery-white lustrous metal is behind the europium zweitreaktivste element of the lanthanides. Superficial injury of the protective oxide layer yellow light the metal. Above 150 ° C, it burns with vigorous glow to the cerium. With water it reacts to the cerium hydroxide.

seltene-erden-cer, Cerium

Cerium is in compounds as trivalent or tetravalent colorless yellow to orange colored cation.

Under the influence of heat it is attacked by ethanol and water very strong. In alkaline solutions, it is strongly attacked with the formation of cerium hydroxide. It is dissolved in acids to form salts.
Since the chemical properties of the rare earths are similar, metallic cerium is rarely used in pure form, but in the mixture, in which it occurs in the production of the rare-earth minerals, the so-called mixed-metal.

Cer ist, Like all lanthanides, slightly toxic. Metallic cerium may be starting 65 ° C ignite. As a finely divided metal can heat up in the air without energy supply, and finally catch fire. The flash is dependent u. a. very strongly on the grain size distribution and the degree. Cerbrände not be extinguished with water, since gaseous hydrogen developed.

Use

Cerium is used in metallurgy as an additive for aluminum alloys and high temperature-resistant iron-base alloys. It assists in the melting process, the separation of sulfur and oxygen. The iron mixed metal alloy mischmetal serves as starting material for use in flints for lighters and producing sparks on roller coasters and movie scenes (Accident scenes). Mischmetal in the composition 70% Cer und 30% Require, known as Auermetall, by Karl Auer von Welsbach, 1903 Patent Pending. A modification was spread worldwide as a flint for lighters.

Small admixtures of (more or less pure) Cerium compounds other materials impart certain properties:

  1. Cerdioxid (CeO ²) is used to stabilize the ceramic catalyst carrier of aluminum oxide used for automotive catalytic converters.
  2. Part of some special glasses, For example, UV filters and windshield, and dehazers in glass production
  3. For staining of enamel
  4. Ceria is used as a polishing agent in glass processing
  5. Cerium-doped fluorescent dyes (Phosphors) in picture tubes and white light-emitting diodes
  6. as a dopant in mantles
  7. Self-cleaning ovens contain a coating cerhaltige
  8. Heaven(IV)-sulfate as an oxidizing agent in quantitative analysis (Cerimetrie)
  9. as contrast agents in magnetic resonance
  10. as a phosphor in gas discharge tubes
  11. added to the regeneration of particulate filters dissolved in the fuel
  12. as part of non-precious metal alloys in dentistry (Ceramics)
  13. as an oxidant for organic synthesis with CAN (Cerium ammonium nitrat), (NH4)² It(NO ³)6
General
Name, Symbol, Number Heaven, EC, 58
Series Lanthanides
group, Period, Block The, 6, f
Appearance silvery white
CAS-Nummer 7440-45-1
Mass fraction of element 43ppm
Atomic
Atomic mass 140,116 you
Atomradius 185 pm
Kovalenter Radius 204 pm
Elektronenkonf. [Car] 4f1 5d1 6s2
1. Ionization 534,4 KJ / mol
2. Ionization 1050 KJ / mol
3. Ionization 1949 KJ / mol
4. Ionization 3547 KJ / mol
Physically
Physical State fixed
Crystal structure face-centered cubic
Density 6,773 g/cm3 (25 ° C)
Mohs 2,5
Magnetism paramagnetisch (χm = 1,4 · 10−3)
Melting point 1068 K (795 C)
Boiling point 3633 K (3360 C)
Molar Volume 20,69 * 10(-6)m(3)/mol
Heat of vaporization 350 KJ / mol
Schmelzwärme 5,5 KJ / mol
Speed ​​of sound 2100 m / s at 293,15 K
Electrical conductivity 1,35*10(6) A/(V * m)
Thermal conductivity 11 W /(m*K)


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