|Name , symbol , atomic number||Cer, Ce, 58|
|Group , period , block||La , 6 , f|
|Mass fraction of the earth's envelope||43 ppm|
|Atomic mass||140.116 (1) and|
|Atomic radius||185 pm|
|Covalent radius||204 pm|
|Electron configuration||[ Xe ] 4 f 1 5 d 1 6 s 2|
|1. Ionization energy||5.5386 (4) eV ≈ 534.39 kJ / mol|
|2. Ionization energy||10.956 (20) eV ≈ 1 057.09 kJ / mol|
|3. Ionization energy||20th.1974 (25) eV ≈ 1 948.75 kJ / mol|
|4. Ionization energy||36.906 (9) eV ≈ 3 560.9 kJ / mol|
|5. Ionization energy||65.55 (25) eV ≈ 6 320 kJ / mol|
|Crystal structure||Cubic area-centered|
|density||6.773 g / cm 3 (25 ° C )|
|magnetism||paramagnetic ( Χ m = 1.4 10 −3 )|
|Melting point||1068 K (795 ° C)|
|boiling point||3743 K (3470 ° C)|
|Molar volume||20.69 · 10 −6 m 3 · mol −1|
|Heat of evaporation||398 kJ / mol|
|Heat of fusion||5.5 kJ mol −1|
|Speed of sound||2100 m s −1 at 293.15 K.|
|Electric conductivity||1.35 · 10 6 A · V −1 · m −1|
|Thermal conductivity||11 W m −1 K −1|
|Oxidation states||3 , 4|
|Normal potential||−2.34 V (Ce 3+ + 3 e - → Ce)|
|Electronegativity||1.12 ( Pauling scale )|
|For other isotopes see list of isotopes|
As far as possible and customary, SI units are used.
Unless otherwise noted, the data given apply to standard conditions .
Cer [ t͡seːɐ̯ (also] cerium or 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 the lanthanides and is also one of the rare earth metals .
Cer was discovered in 1803 by Jöns Jakob Berzelius and Wilhelm von Hisinger and at the same time by Martin Heinrich Klaproth . It was named after the dwarf planet Ceres . Carl Gustav Mosander succeeded in producing the element in 1825 by reducing the chloride with sodium .
In nature, cerium occurs together with other lanthanoids in so-called cerite earths , such as in allanite (Ca, Ce, La, Y) 2 (Al, Fe) 3 (SiO 4 ) 3 (OH), in monazite (Ce, La , Th, Nd, Y) PO 4 as well as in the bastnäsite (Ce, La, Y) CO 3 F. Cer is the most common element of the lanthanides and is ranked 28th in the element frequency in the earth's crust, down to a depth of 16 km calculated, it is represented at 68 g / t and is therefore more common than tin or lead. Important deposits are located in Scandinavia, the USA, the Congo, South Africa and India. The world-wide known cerium reserves are estimated at 40 million tons. Cerium is one of the so-called light rare earths that the BGR assessed in 2014 as uncritical with regard to the supply situation. Elemental (“solid”) cerium does not occur on earth because of its high reactivity. However, it has been found in microscopic particles in lunar rocks. It is probably caused by impact events on the moon.
Extraction and manufacture
After a complex separation of the cerium companion, the oxide is converted with hydrogen fluoride to cerium fluoride . It is then reduced to cerium with calcium to form calcium fluoride . The removal of remaining calcium residues and impurities takes place in an additional remelting process in a vacuum. The annual world production is around 24,000 t.
Four modifications of cerium are known:
The silvery white shiny metal is the second most reactive element of the lanthanoids after europium . Above 150 ° C it burns with a violent glow to form ceria . It reacts with water to form cerium (III) hydroxide .
Cerium occurs in compounds as a trivalent colorless or tetravalent yellow to orange-colored cation .
Since the chemical properties of the rare earths are similar, metallic cerium is rarely used in its pure form, but in the mixture in which it is obtained during manufacture from the rare earth minerals, the so-called mischmetal .
- In metallurgy , mischmetal is used as an additive for aluminum alloys and high-temperature-resistant iron-based alloys . It supports the separation of sulfur and oxygen in the melting process .
- The iron-mixed metal alloy Cereisen serves as a raw material for flints for use in lighters and for generating sparks on roller coasters and in movie scenes (accident scenes).
Small amounts of (more or less pure) cerium compounds give other materials certain properties:
- Ceria (CeO 2 ) is used to stabilize the ceramic catalyst carrier made of aluminum oxide for automobile exhaust catalysts
- Part of some special glasses , for example UV filters and windscreens , and opacifier in glass production
- For coloring enamel
- Ceria is used as a polishing agent in glass processing
- Cer-doped fluorescent dyes ( phosphors ) in picture tubes and white light-emitting diodes
- as doping in incandescent mantles
- Self-cleaning ovens contain a cerium-containing coating
- Cerium (IV) sulfate as an oxidizing agent in quantitative analysis ( cerimetry )
- as a contrast medium in nuclear resonance
- as a fluorescent substance in gas discharge tubes
- for the regeneration of soot particle filters dissolved in the fuel
- It is offered as an oxide cathode for testing purposes as CerHexaBorid (reference: https://www.sindlhauser.de/lab6-keramik-und-kathoden.html )
- as part of non-precious metal-containing bonding alloys in dental technology ( ceramics )
- as an oxidizing agent for organic syntheses with CAN (Cerium ammonium nitrate), (NH 4 ) 2 Ce (NO 3 ) 6
- as a catalyst component for splitting CO 2 . A research team led by Dr. Dorna Esrafilzadeh of RMIT University in Melbourne uses cerium as a component in a liquid metal catalyst to split the greenhouse gas CO 2 into carbon and oxygen at room temperature . The catalytically used liquid metal alloy consisting of gallium , indium , tin and cerium serves as a conductor and electrolyte . In the chemical process, the trivalent cation (Cer 3+ ) is reduced to the metallic cerium .
In 2013, an enzyme that requires cerium ions for its function was first discovered in bacteria . The bacteria of the species Methylacidiphilum fumariolicum were isolated from volcanic mud pools in Italy. You need cerium to build up methanol dehydrogenase , an enzyme in methane metabolism . The ion has the role that calcium ions take over in similar enzymes in other bacteria.
Like all lanthanoids, cerium is slightly toxic. Metallic cerium can ignite from 65 ° C. As a finely divided metal, it can heat up in the air without the use of energy and finally ignite. The readiness for ignition depends u. a. very much on the grain size and the degree of distribution. Cerfires must not be extinguished with water, as gaseous hydrogen develops.
- Cerium (III) oxide Ce 2 O 3 , shiny gold ceramic solid
- Cerium (IV) oxide CeO 2
- Cerium (III, IV) oxide Ce 3 O 4 , blue ceramic solid
- Cerium (III) fluoride CeF 3
- Cerium (IV) fluoride CeF 4
- Cerium (III) chloride CeCl 3 · 7 H 2 O, white, strongly hygroscopic substance
- Cerium (III) bromide CeBr 3
- Cerium (III) iodide CeI 3
- Cerium (III) sulfate Ce 2 (SO 4 ) 3 · 8 H 2 O, colorless substance
- Cerium (IV) sulfate Ce (SO 4 ) 2 , yellow substance
- Cerium (III) nitrate Ce (NO 3 ) 3 · 6 H 2 O
- Cerium (III) oxalate Ce 2 (C 2 O 4 ) 3 · 10 H 2 O
- Ammonium cerium (IV) nitrate (CAN) (NH 4 ) 2 Ce (NO 3 ) 6 , orange-red
- Ammonium cerium (IV) sulfate (NH 4 ) 4 Ce (SO 4 ) 4 · H 2 O
- Cerium (IV) perchlorate Ce (ClO 4 ) 4
- Harry H. Binder: Lexicon of the chemical elements. S. Hirzel Verlag, Stuttgart 1999, ISBN 3-7776-0736-3 .
- The values of the atomic and physical properties (info box) are (unless otherwise stated) taken from www.webelements.com (Cer) .
- CIAAW, Standard Atomic Weights Revised 2013 .
- entry on cerium in Kramida, A., Ralchenko, Yu., Reader, J. and NIST ASD Team (2019): NIST Atomic Spectra Database (ver. 5.7.1) . Ed .: NIST , Gaithersburg, MD. doi : 10.18434 / T4W30F ( https://physics.nist.gov/asd ). Retrieved June 11, 2020.
- Entry on cerium at WebElements, https://www.webelements.com , accessed on June 11, 2020.
- NN Greenwood, A. Earnshaw: Chemistry of the elements. 1st edition. VCH, Weinheim 1988, ISBN 3-527-26169-9 , p. 1579.
- Robert C. Weast (Ed.): CRC Handbook of Chemistry and Physics . CRC (Chemical Rubber Publishing Company), Boca Raton 1990, ISBN 0-8493-0470-9 , pp. E-129 to E-145. Values there are based on g / mol and given in cgs units. The value specified here is the SI value calculated from it, without a unit of measure.
- Yiming Zhang, Julian RG Evans, Shoufeng Yang: Corrected Values for Boiling Points and Enthalpies of Vaporization of Elements in Handbooks. In: Journal of Chemical & Engineering Data . 56, 2011, pp. 328-337, doi: 10.1021 / je1011086 .
- Federal Institute for Geosciences and Raw Materials: Current BGR research: China's share of global rare earth production is falling only slowly. March 12, 2014.
- MMTA: Minor Metals in the Periodic Table: Ce .
- Harry H. Binder: Lexicon of the chemical elements , S. Hirzel Verlag, Stuttgart 1999, ISBN 3-7776-0736-3 , p. 145.
- Arne Grävemeyer: CO2 into coal at room temperature ; heise online, March 8, 2019 - https://www.heise.de/newsticker/meldung/CO2-wird-zu-Kohle-bei-Raum Temperatur-4329963.html
- Robert F.Service: New way to turn carbon dioxide into coal Could 'rewind the clock emissions' . In: Science , February 27, 2019 doi : 10.1126 / science.aax1527
- Esrafilzadeh et al .: Room temperature CO2 reduction to solid carbon species on liquid metals featuring atomically thin ceria interfaces . In: Nature Communications 10, 865 (2019)
- Arjan Pol, Thomas RM Barends et al. a .: Rare earth metals are essential for methanotrophic life in volcanic mudpots. In: Environmental Microbiology. 2013, pp. N / a – n / a, doi: 10.1111 / 1462-2920.12249 .