Cerium (Ce)
lanthanideSolid
Peso atomico standard
140,116 uConfigurazione elettronica
[Xe] 6s2 4f1 5d1Punto di fusione
797,85 °CPunto di ebollizione
3423,85 °CDensità
6770 kg/m³Stati di ossidazione
+1, +2, +3, +4Elettronegatività (Pauling)
1,12Energia di ionizzazione (1ª)
5,5386 eVAnno della scoperta
1801Raggio atomico
185 pmDettagli
Cerium is the first lanthanide by atomic number and one of the most abundant rare-earth elements in the crust. It is a reactive, electropositive metal whose chemistry is unusual among lanthanides because both Ce³⁺ and Ce⁴⁺ are accessible in ordinary compounds. This Ce³⁺/Ce⁴⁺ redox pair, especially in oxides, makes cerium important in catalysts, polishing materials, glass treatment, and oxygen-storage applications.
Cerium is especially interesting because of its variable electronic structure. The energy of the inner 4f level is nearly the same as that of the outer (valence) electrons, and only small amounts of energy are required to change the relative occupancy of these electronic levels. This gives rise to dual valency states.
For example, a volume change of about 10 percent occurs when cerium is subjected to high pressures or low temperatures. Cesium's valence appears to change from about 3 to 4 when it is cooled or compressed. The low temperature behavior of cerium is complex.
Cerium is an iron-gray lustrous metal. It is malleable, and oxidizes very readily at room temperature, especially in moist air. Except for europium, cerium is the most reactive of the rare-earth metals. It decomposes slowly in cold water and rapidly in hot water.
Alkali solutions and dilute and concentrated acids attack the metal rapidly. The pure metal is likely to ignite if scratched with a knife.
Ceric slats are orange red or yellowish; cerous salts are usually white.
The name derives from the planetoid Ceres, which was discovered by the Italian astronomer Giuseppe Piazzi in 1801 and named for Ceres, the Roman goddess of agriculture and harvest. Two years later, the element cerium was discovered by the German chemist Martin-Heinrich Klaproth, who called it ochroeite earth because of its yellow colour.
Cerium was independently discovered at the same time by the Swedish chemist Jöns Jacob Berzelius and the Swedish mineralogist Wilhelm von Hisinger, who called it ceria. It was first isolated in 1875 by the American mineralogist and chemist William Frances Hillebrand and the American chemist Thomas H. Norton.
Cerium was discovered by Jöns Jacob Berzelius and Wilhelm von Hisinger, Swedish chemists, and independently by Martin Heinrich Klaproth, a German chemist, in 1803. Cerium is the most abundant of the rare earth elements and makes up about 0.0046% of the earth's crust. Today, cerium is primarily obtained through an ion exchange process from monazite sand ((Ce, La, Th, Nd, Y)PO4), a material rich in rare earth elements.
Cerium was named for the asteroid Ceres, which was discovered in 1801. The element was discovered two years later in 1803 by Klaproth and by Berzelius and Hisinger. In 1875 Hillebrand and Norton prepared the metal.
Pure cerium is a soft, silvery-gray metal that tarnishes readily in air. Fresh surfaces are metallic and bright, but oxidation quickly dulls them. The metal is ductile at room temperature, relatively low-melting for a lanthanide, and reactive enough that small particles can ignite when heated or abraded.
Cerium is widely used as cerium dioxide, CeO₂, in glass polishing powders and as an oxygen-storage component in automotive catalytic converters. Cerium compounds decolorize glass by oxidizing iron impurities and can also impart ultraviolet absorption. Mischmetal, a rare-earth alloy rich in cerium, is used in lighter flints and spark-producing alloys. Cerium is also used in some aluminum, magnesium, and iron alloys, where small additions can modify microstructure and oxidation behavior.
Pure cerium will ignite if it is scratched with a sharp object, but can be safely used if combined with other materials. Cerium is one of the rare earth elements used to make carbon arc lights which are used in the motion picture industry for studio lighting and projector lights. Cerium is also a component of Misch metal, a material that is used to make flints for lighters. Cerium is also used as a catalyst to refine petroleum and as an alloying agent to make special metals.
Cerium oxide (Ce2O3 and CeO2) is a component of the walls of self cleaning ovens and of incandescent lantern mantles. Cerium oxide is also used to polish glass surfaces. Ceric sulfate (Ce(So4)2) is used in some chemical analysis processes. Other cerium compounds are used to make some types of glass as well as to remove color from glass.
Cerium is a component of misch metal, which is extensively used in the manufacture of pyrophoric alloys for cigarette lighters. While cerium is not radioactive, the impure commercial grade may contain traces of thorium, which is radioactive. The oxide is an important constituent of incandescent gas mantles and is emerging as a hydrocarbon catalyst in self cleaning ovens where it can be incorporated into oven walls to prevent the collection of cooking residues.
As ceric sulfate is used extensively as a volumetric oxidizing agent in quantitative analysis. Cerium compounds are used in the manufacture of glass, both as a component and as a decolorizer.
The oxide is finding increased use as a glass polishing agent instead of rouge, for it polishes much faster than rouge. Cerium, with other rare earths, is used in carbon-arc lighting, especially in the motion picture industry. It is also useful as a catalyst in petroleum refining and in metallurgical and nuclear applications.
Isotopes in Earth/Planetary Science
When combined, 138La– 138Ce and 147Sm– 143Nd are two decay systems that are useful for studying processes affecting the light-rare-earth elements (lanthanum, cerium, praseodymium, neodymium, and samarium) and the igneous evolution of the Moon and Earth because different igneous materials have different cerium isotopic compositions (Fig. IUPAC.58.1) and can be used in mass balance investigations [419] H. Tazoe, H. Obata, T. Gamo. J. Anal. At. Spectrom.22, 616 (2007)., [420] M. Tanimizu, T. Tanaka. Geochim. Cosmochim. Acta66, 4007 (2002)..
Isotopes in Geochronology
138Ce is a radiogenic isotope produced by decay of 138La, with a half-life of 1.06×1011 years, one of the longest clocks in geochronology. Thus, the isotope-amount ratio n(138Ce)/n(142Ce) can be used for dating rocks on long time scales (billions of years) and can also be used as a chemical tracer in geochemical studies.
Isotopes in Medicine
144Ce (with a half-life of 0.78 year) has been used for brachytherapy applications in cells and vessels of the body. The half-life and specific activity of 144Ce give it a potential advantage over the commonly used isotope 192Ir of higher dose rate at shorter distances and lower irradiation of organs outside the tumor [424] V. O. Zilio, O. P. Joneja, Y. Popowski, F. O. Bochud, R. Chawla. Int. J. Radiat. Oncol. Biol. Phys.62, 585 (2005).. 144Ce enables the treatment of larger arteries as compared with 32P, another isotope commonly used for this style of radiotherapy.
Cerium commonly forms trivalent salts containing Ce³⁺ and tetravalent compounds containing Ce⁴⁺. Cerium dioxide, CeO₂, is the most important oxide and can reversibly lose small amounts of oxygen to form nonstoichiometric oxides, a property central to catalysis. Cerium(III) oxide, Ce₂O₃, is stable under reducing conditions. Cerium(III) chloride, CeCl₃, and cerium(III) nitrate, Ce(NO₃)₃, are common starting materials, while ceric ammonium nitrate, (NH₄)₂Ce(NO₃)₆, is a strong one-electron oxidant in laboratory chemistry.
See more information at the Cerium compound page.
Bulk cerium metal has low acute toxicity but is a fire risk as powder, turnings, or dust. It reacts with acids to release H₂ and should be kept from strong oxidizers and moisture when finely divided. Soluble cerium salts can irritate skin, eyes, and the respiratory tract, and inhalation of rare-earth dusts is an occupational concern. Natural cerium is not significantly radioactive for normal handling purposes.
Cerium occurs mainly in rare-earth minerals such as monazite, bastnäsite, and allanite, usually with other lanthanides. In surface environments it is commonly trivalent, but oxidation to Ce⁴⁺ can immobilize it as sparingly soluble oxides and hydroxides. This redox behavior produces cerium anomalies in marine sediments and some rocks, which are used as geochemical indicators of oxidation conditions.
Cerium is obtained as a by-product of rare-earth mining and separation, especially from bastnäsite and monazite concentrates. Because it is relatively abundant compared with many rare earths, supply is often tied more to separation capacity and demand for the whole rare-earth suite than to geological scarcity. Major demand comes from polishing powders, catalysts, glass additives, and pyrophoric alloys. Recycling is limited but possible from spent catalysts and industrial polishing slurries when collection and contamination levels make recovery practical.
Cerium is the most abundant so-called rare-earth metals. It is found in a number of minerals including allanite (also known as orthite), monazite, bastnasite, cerite, and samarskite. Monazite and bastnasite are presently the more important sources of cerium.
Large deposits of monazite (found on the beaches of Travancore, India and in river sands in Brazil), allanite (in the western United States), and bastnasite (in Southern California) will supply cerium, thorium, and the other rare-earth metals for many years to come.
Metallic cerium is prepared by metallothermic reduction techniques, such as reducing cerous fluoride with calcium, or using electrolysis of molten cerous chloride or others processes. The metallothermic technique produces high-purity cerium.
Cerium is made chiefly by neutron-capture processes in evolved stars, including the slow s-process and rapid r-process contributions. It is far less abundant cosmically than iron or oxygen but is one of the more abundant lanthanides. Cerium has been detected spectroscopically in some chemically peculiar stars, where rare-earth lines can be unusually strong.
- Cerium was named after the dwarf planet Ceres, discovered shortly before the element.
- CeO₂ can store and release oxygen without fully changing its crystal framework.
- Cerium is the only lanthanide with a common, stable tetravalent aqueous and solid-state chemistry.
- Finely divided cerium-rich alloys are the sparking material in many lighter flints.
- Cerium can show geochemical anomalies because Ce³⁺ is oxidized more readily than neighboring lanthanides.
Immagini
Proprietà
Fisiche
- Raggio atomico (empirico)
- 185 pm Confronta Raggio atomico (empirico) di tutti gli elementi →
- Raggio covalente
- 204 pm Confronta Raggio covalente di tutti gli elementi →
- Raggio di van der Waals
- 235 pm Confronta Raggio di van der Waals di tutti gli elementi →
- Densità
- 6770 kg/m³ Confronta Densità di tutti gli elementi →
- Volume molare
- 0,021 L/mol
- Fase in condizioni STP
- Solido Confronta Fase in condizioni STP di tutti gli elementi →
- Punto di fusione
- 797,85 °C Confronta Punto di fusione di tutti gli elementi →
- Punto di ebollizione
- 3423,85 °C Confronta Punto di ebollizione di tutti gli elementi →
- Conducibilità termica
- 11,3 W/(m·K) Confronta Conducibilità termica di tutti gli elementi →
- Capacità termica specifica
- 0,192 J/(g·K) Confronta Capacità termica specifica di tutti gli elementi →
- Capacità termica molare
- 26,94 J/(mol·K) Confronta Capacità termica molare di tutti gli elementi →
- Struttura cristallina
- Cubica a facce centrate Confronta Struttura cristallina di tutti gli elementi →
Chimiche
- Elettronegatività (Pauling)
- 1,12 Confronta Elettronegatività (Pauling) di tutti gli elementi →
- Affinità elettronica
- 0,955 eV
- Energia di ionizzazione (1ª)
- 5,5386 eV Confronta Energia di ionizzazione (1ª) di tutti gli elementi →
- Energia di ionizzazione (2ª)
- 10,956038 eV Confronta Energia di ionizzazione (2ª) di tutti gli elementi →
- Energia di ionizzazione (3ª)
- 20,19747 eV Confronta Energia di ionizzazione (3ª) di tutti gli elementi →
- Energia di ionizzazione (4ª)
- 36,906127 eV Confronta Energia di ionizzazione (4ª) di tutti gli elementi →
- Energia di ionizzazione (5ª)
- 65,550226 eV Confronta Energia di ionizzazione (5ª) di tutti gli elementi →
- Stati di ossidazione
- +1, +2, +3, +4 Confronta Stati di ossidazione di tutti gli elementi →
- Elettroni di valenza
- 3 Confronta Elettroni di valenza di tutti gli elementi →
- Configurazione elettronica
- [Xe] 6s2 4f1 5d1
Termodinamiche
- Calore di fusione
- 0,05658911 eV Confronta Calore di fusione di tutti gli elementi →
- Calore di vaporizzazione
- 3,254392 eV Confronta Calore di vaporizzazione di tutti gli elementi →
- Calore di sublimazione
- 4,124994 eV
- Calore di atomizzazione
- 4,124994 eV
- Entalpia di atomizzazione
- 4,354045 eV
Nucleari
- Protoni
- 58 Confronta Protoni di tutti gli elementi →
- Neutroni
- 82 Confronta Neutroni di tutti gli elementi →
- Isotopi noti
- 41 Confronta Isotopi noti di tutti gli elementi →
- Isotopi stabili
- 1 Confronta Isotopi stabili di tutti gli elementi →
- Isotopo più stabile
- Ce-140
- Anno della scoperta
- 1801
Abbondanza
- Abbondanza (crosta terrestre)
- 66,5 mg/kg Confronta Abbondanza (crosta terrestre) di tutti gli elementi →
- Abbondanza (oceano)
- 1,2 × 10−6 mg/L Confronta Abbondanza (oceano) di tutti gli elementi →
Struttura cristallina
- Costante reticolare a
- 516 pm
Struttura elettronica
- Elettroni per guscio
- 2, 8, 18, 19, 9, 2 Confronta Elettroni per guscio di tutti gli elementi →
Identificativi
- Numero CAS
- 7440-45-1 Confronta Numero CAS di tutti gli elementi →
- Simbolo di termine
- 1G°4
- InChI
- InChI=1S/Ce
- Chiave InChI
- GWXLDORMOJMVQZ-UHFFFAOYSA-N
Configurazione elettronica Misurato
Ce: 4f¹ 5d¹ 6s²[Xe] 4f¹ 5d¹ 6s²1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹ 5d¹ 6s²Modello atomico
Gli isotopi modificano il numero di neutroni, la massa e la stabilità — non la configurazione elettronica di un atomo neutro.
Modello atomico schematico, non in scala.
Impronta atomica
Spettro di emissione / assorbimento
Distribuzione isotopica
| Numero di massa | Massa atomica (u) | Abbondanza naturale | Emivita |
|---|---|---|---|
| 140 Stabile | 139,9054431 ± 0,0000023 | 88,4500% | Stabile |
Fase / Stato
Motivo: 772,9 °C sotto il punto di fusione (797,85 °C)
Schema non in scala
Punti di transizione di fase
Energie di transizione
Energia necessaria per fondere 1 mol al punto di fusione
Energia necessaria per vaporizzare 1 mol al punto di ebollizione
Energia necessaria per sublimare 1 mol al punto di sublimazione
Densità
In condizioni standard
In condizioni standard
Spettri atomici
Sono visualizzati 10 di 58. Ordinamento per carica ionica crescente.
Righe disponibili ?
| Ione | Carica | Righe totali | Probabilità di transizione | Designazioni dei livelli |
|---|---|---|---|---|
| Ce I | 0 | 209 | 67 | 209 |
| Ce II | +1 | 560 | 283 | 560 |
| Ce III | +2 | 262 | 0 | 0 |
| Ce IV | +3 | 27 | 0 | 0 |
| Ce V | +4 | 5 | 0 | 0 |
Livelli disponibili ?
| Ione | Carica | Livelli |
|---|---|---|
| Ce I | 0 | 953 |
| Ce II | +1 | 491 |
| Ce III | +2 | 227 |
| Ce IV | +3 | 17 |
| Ce V | +4 | 12 |
| Ce VI | +5 | 4 |
| Ce VII | +6 | 2 |
| Ce VIII | +7 | 2 |
| Ce IX | +8 | 2 |
| Ce X | +9 | 2 |
Raggi ionici
| Carica | Coordinazione | Spin | Raggio |
|---|---|---|---|
| +3 | 6 | N/D | 101 pm |
| +3 | 7 | N/D | 107 pm |
| +3 | 8 | N/D | 114.3 pm |
| +3 | 9 | N/D | 119.6 pm |
| +3 | 10 | N/D | 125 pm |
| +3 | 12 | N/D | 134 pm |
| +4 | 6 | N/D | 87 pm |
| +4 | 8 | N/D | 97 pm |
| +4 | 10 | N/D | 97 pm |
| +4 | 12 | N/D | 113.99999999999999 pm |
Composti
Isotopi (1)
| Numero di massa | Massa atomica (u) | Abbondanza naturale | Emivita | Modalità di decadimento | |
|---|---|---|---|---|---|
| 140 Stabile | 139,9054431 ± 0,0000023 | 88,4500% ± 0,0510% | Stabile | stable |
Proprietà estese
Raggi covalenti (dati estesi)
- Raggio covalente (Pyykkö)
- 163 pm
- Raggio covalente (Pyykkö, legame doppio)
- 137 pm
- Raggio covalente (Pyykkö, legame triplo)
- 131 pm
Raggi di van der Waals
- Alvarez
- 288 pm
- UFF
- 355,6 pm
- MM3
- 274 pm
Raggi atomici e metallici
- Raggio atomico (Rahm)
- 282 pm
Scale di numerazione
- Mendeleev
- 15
- Pettifor
- 32
- Glawe
- 31
Scale di elettronegatività
- Ghosh
- 0
- Miedema
- 3
- Gunnarsson–Lundqvist
- 4
- Robles–Bartolotti
- 3
Polarizzabilità e dispersione
- Polarizzabilità dipolare
- 205 a.u.
- Polarizzabilità dipolare (inc.)
- 20 a.u.
- C₆ (Gould–Bučko)
- 3480 Ha·Bohr6
Parametri di Miedema
- Volume molare di Miedema
- 21,62 cm3/mol
- Densità elettronica di Miedema
- 2
Rischio di approvvigionamento ed economia
- Concentrazione della produzione
- 97
- Rischio relativo di approvvigionamento
- 10
- Distribuzione delle riserve
- 50
- Stabilità politica (principale produttore)
- 24
- Stabilità politica (principale detentore di riserve)
- 24
Transizioni di fase e allotropi
| Punto di fusione | 1072,15 K |
| Punto di ebollizione | 3716,15 K |
Categorie degli stati di ossidazione
Dati di riferimento avanzati
Costanti di schermaggio (13)
| n | Orbitale | σ |
|---|---|---|
| 1 | s | 1,1519 |
| 2 | p | 4,2176 |
| 2 | s | 15,26 |
| 3 | d | 13,9147 |
| 3 | p | 19,0405 |
| 3 | s | 19,3408 |
| 4 | d | 32,3392 |
| 4 | f | 56,324 |
| 4 | p | 29,3936 |
| 4 | s | 28,32 |
Dettaglio dei raggi cristallini (10)
| Carica | CN | Spin | rcrystal (pm) | Origine |
|---|---|---|---|---|
| 3 | VI | 115 | from r^3 vs V plots, | |
| 3 | VII | 121 | estimated, | |
| 3 | VIII | 128,3 | from r^3 vs V plots, | |
| 3 | IX | 133,6 | from r^3 vs V plots, | |
| 3 | X | 139 | ||
| 3 | XII | 148 | calculated, | |
| 4 | VI | 101 | from r^3 vs V plots, | |
| 4 | VIII | 111 | from r^3 vs V plots, | |
| 4 | X | 121 | from r^3 vs V plots, | |
| 4 | XII | 128 |
Modalità di decadimento degli isotopi (54)
| Isotopo | Modalità | Intensità |
|---|---|---|
| 119 | B+ | — |
| 119 | B+p | — |
| 120 | B+ | — |
| 120 | B+p | — |
| 121 | B+ | 100% |
| 121 | B+p | 1% |
| 122 | B+ | — |
| 122 | B+p | — |
| 123 | B+ | 100% |
| 123 | B+p | — |
Fattori di diffusione dei raggi X (508)
| Energia (eV) | f₁ | f₂ |
|---|---|---|
| 10 | — | 1,28369 |
| 10,1617 | — | 1,26389 |
| 10,3261 | — | 1,24441 |
| 10,4931 | — | 1,22522 |
| 10,6628 | — | 1,20632 |
| 10,8353 | — | 1,18772 |
| 11,0106 | — | 1,16941 |
| 11,1886 | — | 1,15138 |
| 11,3696 | — | 1,13362 |
| 11,5535 | — | 1,11614 |
Dati aggiuntivi
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
6.65×101 milligrams per kilogram
Riferimenti (1)
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
1.2×10-6 milligrams per liter
Riferimenti (1)
Sources
Sources of this element.
Cerium is the most abundant so-called rare-earth metals. It is found in a number of minerals including allanite (also known as orthite), monazite, bastnasite, cerite, and samarskite. Monazite and bastnasite are presently the more important sources of cerium.
Large deposits of monazite (found on the beaches of Travancore, India and in river sands in Brazil), allanite (in the western United States), and bastnasite (in Southern California) will supply cerium, thorium, and the other rare-earth metals for many years to come.
Metallic cerium is prepared by metallothermic reduction techniques, such as reducing cerous fluoride with calcium, or using electrolysis of molten cerous chloride or others processes. The metallothermic technique produces high-purity cerium.
Riferimenti (1)
- [6] Cerium https://periodic.lanl.gov/58.shtml
Riferimenti
(9)
Data deposited in or computed by PubChem
The half-life and atomic mass data was provided by the Atomic Mass Data Center at the International Atomic Energy Agency.
Element data are cited from the Atomic weights of the elements (an IUPAC Technical Report). The IUPAC periodic table of elements can be found at https://iupac.org/what-we-do/periodic-table-of-elements/. Additional information can be found within IUPAC publication doi:10.1515/pac-2015-0703 Copyright © 2020 International Union of Pure and Applied Chemistry.
The information are cited from Pure Appl. Chem. 2018; 90(12): 1833-2092, https://doi.org/10.1515/pac-2015-0703.
Thomas Jefferson National Accelerator Facility (Jefferson Lab) is one of 17 national laboratories funded by the U.S. Department of Energy. The lab's primary mission is to conduct basic research of the atom's nucleus using the lab's unique particle accelerator, known as the Continuous Electron Beam Accelerator Facility (CEBAF). For more information visit https://www.jlab.org/
The periodic table at the LANL (Los Alamos National Laboratory) contains basic element information together with the history, source, properties, use, handling and more. The provenance data may be found from the link under the source name.
The periodic table contains NIST's critically-evaluated data on atomic properties of the elements. The provenance data that include data for atomic spectroscopy, X-ray and gamma ray, radiation dosimetry, nuclear physics, and condensed matter physics may be found from the link under the source name. Ref: https://www.nist.gov/pml/atomic-spectra-database
This section provides all form of data related to element Cerium.
The element property data was retrieved from publications.