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Cerium
Discovered in 1803 by J.J. Berzelius and W. Hisinger at Vestmanland,
Sweden. First isolated by W.F. Hilebrand and T.H. Norton in 1875 at Washington DC, USA.
[Named after the asteroid Ceres discovered in 1801]
French: cérium
German: Cer
Italian: cerio
Spanish: cerio
Description: Cerium is
a reactive, grey metal and is the most abundant of the so-called rare earth
metals (more correctly termed the landthanides). It tarnishes in air, burns
easily if ignited, reacts rapidly with water, and disolves in acids. Cerium is
used in glass, flints, ceramics and alloys.
Materials properties
| Density: |
8240(a); 6749(b); 6773(g); 6700(d) kg/m-3 [298 K] |
| Melting point: |
1072 °K |
| Boiling point: |
3699 °K |
| Molar volume: |
17.00 cm3 |
| Thermal conductivity: |
11.4 [300 K] Wm-1K-1 |
| Coefficient of linear thermal expansion: |
8.5 x 10-6 K-1 |
| Electrical resistivity: |
73 x 10-8 [273 K] Wm |
| 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 |
| Radii: |
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 |
| Issotope 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 p.p.m. |
| Liver: |
0.29 p.p.m. |
| Muscle: |
n.a. |
| Daily dietary intake: |
n.a. but very low |
| Total mass of element in average [70 kg] person: |
40 mg |
Crystal data
| Crystal structure, (cell dimentions / pm), space group |
α-Ce f.c.c. (a = 485), Fm3m
β-Ce hexagonal (a = 367.3, c = 1180.2), P63/mmc
γ-Ce f.c.c. (a = 516.01), Fm3m
δ-Ce f.c.c. (a = 412), Im3m
T(β->γ)= 441 K |
| X-ray diffraction: mass absorption coefficients (µ/ρ)/cm2g-1 : |
CuKα 352 MoKα 48.2 |
| Neutron scattering length, b/10-12cm: |
0.484 |
| Thermal neutron capture cross-section, σa/barns : |
0.6 |
Geological data
| Mineral |
Formula |
Density |
Hardness |
Crystal apperance |
| Bastanäsite-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 praticularly rich in cerium.
| Chief ore: |
>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. Safe. |
| Abundances |
|
| Sun: |
35.5 (relative to H = 1 x 1023) |
| Earth's crust: |
68 p.p.m. |
| Seawater: |
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| Atlantic surface: |
9.0 x 10-6 p.p.m. |
| Atlantic deep: |
2.6 x 10-6 p.p.m. |
| Pacific surface: |
1.5 x 10-6 p.p.m. |
| Pacific deep: |
0.5 x 10-6 p.p.m. |
| Residence time: |
100 years |
| Classification: |
scavenged |
| Oxidation state: |
III |
Other sizes and specifications on request
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