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Cer (Ce)
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Cer 58Ce140.115
1803 von J.J. Berzelius und W. Hisinger in Vestmanland, Schweden, entdeckt. Zuerst dargestellt von W.F. Hillebrand und T.H. Norton 1875 in Washington, DC, USA.
[Nach dem 1801 entdeckten Planetoiden Ceres bennant]
French: cérium
English: cerium
Italian: cerio
Spanish: cerio
Beschreibung: Reaktives, graues Metall, das häufigste Lanthanoid. Läuft in Luft an, verbrennt beim Erhitzen, reagiert heftig mit Wasser, löst sich in Säuren. Verwendet für Gläser, Feuersteine, Keramiken und Legierungen.
Further Materials properties
| Crystal structure: |
(cell dimensions/pm), space group, |
|---|---|
| X-ray diffractions mass absorption coefficients: | CuKa 352 (µ/r) / cm2g-1 MoKa 48.2 (µ/r) / cm2g-1 |
| Neutron scattering length: | 0.484 b/10-12 cm |
| Thermal neutron capture cross-section: | 0.6 sa / barns |
| Density: | 8240 (a); 6749 (β); 6773 (γ); 6700 (δ) kg/m-3 [293 K] |
| Melting point: | 798,85°C / 1072 °K |
| Boiling point: | 3425,85°C / 3699 °K |
| Molar volume: | 17.00 cm3 |
| Thermal conductivity: | 11.4 [300 K] W m-1K-1 |
| Coefficient of linear thermal expansion: | 8.5 x 10-6 K-1 |
| Electrical resistivity: | 73 x 10-8 [273 K] Ωm |
| Mass magnetic susceptibility: | +2.17 x 10-7(s) kg-1m3 |
| Young's modulus: | 33.5 GPa |
| Rigidity modulus: | 13.5 GPa |
| Bulk modulus: | n.a. |
| Poisson's ratio: | 0.248 GPa |
| Radi: | Ce4+ 94;Ce3+ 107; atomic 182.5; covalent 165 |
| Electronegativity: | 1.12 (Pauling); 1.06 (Allred); ≤3.0 eV (absolute) |
| Effective nuclear charge: | 2.85 (Slater); 10.80 (Clementi); 10.57 (Froese-Fischer) |
| Number of Isotopes (incl. nuclear isomers): | 28 |
| Isotope mass range: | 129 -> 151 |
Biological data
| Biological role: | None, but acts to stimulate metabolism. |
|---|---|
| Toxicity | |
| Toxic intake: | n.a. |
| Lethal intake: | LD50 (chloride, oral, mouse) = 2100 mg Kg-1 |
| Hazards: | Cerium is mildly toxic by ingestion, but insoluble salts, such as the oxalate, are non-toxic and doses of up to 500 mg were once prescribed to prevent travel sickness and morning sickness. |
| Level in humans | |
| Blood: | < 0.002 mg dm-3 |
| Bone: | 2.7 ppm |
| Liver: | 0.29 ppm |
| Muscle: | n.a. |
| Daily dietary intake: | n.a. but very low |
| Total mass of element in average [70 kg] person: |
40 mg |
Geological data
| Minerals: | ||||
|---|---|---|---|---|
| Mineral | Formula | Density | Hardness | Crystal apperance |
| Bastnäsite-Ce* | (Ce, La, etc.) CO3F | 4.9 | 4 - 4.5 | hex., vit/ greasy yellow |
| Monazite-Ce* | (Ce, La, Nd, Th, etc.)PO4 | 5.20 | 5 - 5.5 | mon., waxy/ vit. yellow-brown |
* Varieties of these minerals that are particularly rich in cerium
| Chief ores: | monazite, bastnäsite. Perovskite (Ti mineral) can also be rich in cerium |
|---|---|
| World production: | 24 000 tonnes/year |
| Main mining areas: | USA, Brazil, India, Sri Lanka, Australia, China |
| Reserves: | c. 15 x 106 tonnes |
| Specimen: | available as chips, ingots or powder. Safer. |
| Abundances | |
|---|---|
| Sun: | 35.5 (relative to H = 1 x 1012) |
| Earth's crust: | 68 ppm |
| Seawater | |
| Altantic surface: | 9.0 x 10-6 ppm |
| Atlantic deep: | 2.6 x 10-6 ppm |
| Pacific surface: | 1.5 x 10-6 ppm |
| Pacific deep: | 0.5 x 10-6 ppm |
| Residence time: | 100 years |
| Classification: | scavenged |
| Oxidation state: | III |
Source: Emsley, J. (1998) The Elements (3rd Edition)
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