Cerium

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Cerium,  58Ce
General properties
Name, symbol Cerium, Ce
Appearance Silvery white
Cerium in the periodic table


Ce

Th
LanthanumCeriumPraseodymium
Atomic number 58
Standard atomic weight (Ar) 140.116(1)
Group, block , f-block
Period period 6
Electron configuration [Xe] 4f1 5d1 6s2
per shell
2, 8, 18, 19, 9, 2
Physical properties
Silvery-white
Phase Solid
Melting point 1068 K ​(795 °C, ​​1463 °F)
Boiling point 3716​ K ​(3443 °C, ​6229 °F)
Density near r.t. 6.77 g/cm3
when liquid, at  6.55 g/cm3
Heat of fusion 5.46 kJ/mol
Heat of 398 kJ/mol
Molar heat capacity 26.94 J/(mol·K)
 pressure
Atomic properties
Oxidation states 4, 3, 2, 1 ​(a mildly basic oxide)
Electronegativity Pauling scale: 1.12
energies 1st: 534.4 kJ/mol
2nd: 1050 kJ/mol
3rd: 1949 kJ/mol
Atomic radius empirical: 181.8 pm
Covalent radius 204±9 pm
Miscellanea
Crystal structureβ-Ce
Double hexagonal close-packed (dhcp)
γ-Ce
Face-centered cubic (fcc)
Speed of sound thin rod 2,100 m/s (at 20 °C)
Thermal expansion 6.3 µm/(m·K) (γ, poly)
Thermal conductivity 11.3 W/(m·K)
Electrical resistivity 828·10-9 Ω·m (at 20 °C) (β, poly)
Magnetic ordering Paramagnetic
Young's modulus 33.6 GPa (γ-Ce)
Shear modulus 13.5 GPa (γ-Ce)
Bulk modulus 21.5 GPa (γ-Ce)
Poisson ratio 0.24 (γ-Ce)
Mohs hardness 2.5
Vickers hardness 210–470 MPa
Brinell hardness 186–412 MPa
CAS Registry Number 7440-45-1
History
Naming After dwarf planet Ceres, itself named after Roman deity of agriculture Ceres
Discovery Martin Heinrich Klaproth, Jöns Jakob Berzelius, Wilhelm Hisinger (1803)
First isolation Carl Gustaf Mosander (1838)
· references

Cerium is a chemical element with symbol Ce and atomic number 58. It is one of the most abundant rare earth metals, one of the easiest to separate, and one of the easiest to purchase. It is notable by its high propensity for sparking when struck, making it an ideal material for firestarters in the alloys ferrocerium and mischmetal.

Properties

Chemical

Cerium metal tarnishes slowly in air and burns readily at 150 °C to form cerium(IV) oxide:

Ce + O2 → CeO2

Cerium reacts with all halogens to form trihalides. Cerium will slowly react with water.

Cerium is notable among the lanthanides due to the existence of a cerium(III) (cerous) state and cerium(IV) (ceric) state. While cerous compounds are usually colorless or white, and form colorless complexes as well, cerric salts usually present a yellow, orange, or red coloration. Cerium(IV) sulfate is a strong oxidizing agent which can oxidize hydrogen peroxide to oxygen and water. Ceric ammonium sulfate is a commonly available from lab suppliers.

Physical

Cerium is a grey silvery metal, soft, and both malleable and ductile. Cerium has the third-longest liquid range of any element, after thorium and uranium: 2648 °C (795 °C to 3443 °C). It sparks readily when cut, ground, or struck.

Availability

Cerium can be purchased from GalliumSource. 30 g costs US$55. It can also be found in ferrocerium firestarters, though due to its high reactivity, the extraction process is complex and required reduction with a more reactive metal, such as calcium.

Preparation

Cerium can be prepared by reducing its oxide with lithium or calcium, but this is impractical compared to simply purchasing a sample of the metal.

Projects

  • Ferrocerium
  • Use as an oxidizer

Safety and storage

Safety

Cerium metal is not known to be toxic, but it is a relatively large fire hazard due to its tendency to spark. Even sanding or filing a sample by hand can cause a significant amount of sparking and ignite flammable objects. These sparks are quite large and may include small globs of burning metal. Cerium fires should never be put out with water as it may cause a hydrogen explosion. Cerium and mischmetal fires have a distinct smell that has both a metallic and smoky quality.

Storage

Cerium corrodes relatively easily and should be stored in an airtight container under mineral oil or argon.

Disposal

Cerium compounds present little toxicity and can be safely disposed of. However, due to the high price of lanthanides, it's better to try to recycle them.

References

Relevant Sciencemadness threads