Cerium (Ce)
lanthanideSolid
Peso atômico padrão
140,116 uConfiguração eletrônica
[Xe] 6s2 4f1 5d1Ponto de fusão
797,85 °CPonto de ebulição
3423,85 °CDensidade
6770 kg/m³Estados de oxidação
+1, +2, +3, +4Eletronegatividade (Pauling)
1,12Energia de ionização (1ª)
5,5386 eVAno da descoberta
1801Raio atômico
185 pmDetalhes
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.
Imagens
Propriedades
Física
- Raio atômico (empírico)
- 185 pm Comparar Raio atômico (empírico) de todos os elementos →
- Raio covalente
- 204 pm Comparar Raio covalente de todos os elementos →
- Raio de van der Waals
- 235 pm Comparar Raio de van der Waals de todos os elementos →
- Densidade
- 6770 kg/m³ Comparar Densidade de todos os elementos →
- Volume molar
- 0,021 L/mol
- Fase nas CNTP
- Sólido Comparar Fase nas CNTP de todos os elementos →
- Ponto de fusão
- 797,85 °C Comparar Ponto de fusão de todos os elementos →
- Ponto de ebulição
- 3423,85 °C Comparar Ponto de ebulição de todos os elementos →
- Condutividade térmica
- 11,3 W/(m·K) Comparar Condutividade térmica de todos os elementos →
- Capacidade calorífica específica
- 0,192 J/(g·K) Comparar Capacidade calorífica específica de todos os elementos →
- Capacidade calorífica molar
- 26,94 J/(mol·K) Comparar Capacidade calorífica molar de todos os elementos →
- Estrutura cristalina
- Cúbica de faces centradas Comparar Estrutura cristalina de todos os elementos →
Química
- Eletronegatividade (Pauling)
- 1,12 Comparar Eletronegatividade (Pauling) de todos os elementos →
- Afinidade eletrônica
- 0,955 eV
- Energia de ionização (1ª)
- 5,5386 eV Comparar Energia de ionização (1ª) de todos os elementos →
- Energia de ionização (2ª)
- 10,956038 eV Comparar Energia de ionização (2ª) de todos os elementos →
- Energia de ionização (3ª)
- 20,19747 eV Comparar Energia de ionização (3ª) de todos os elementos →
- Energia de ionização (4ª)
- 36,906127 eV Comparar Energia de ionização (4ª) de todos os elementos →
- Energia de ionização (5ª)
- 65,550226 eV Comparar Energia de ionização (5ª) de todos os elementos →
- Estados de oxidação
- +1, +2, +3, +4 Comparar Estados de oxidação de todos os elementos →
- Elétrons de valência
- 3 Comparar Elétrons de valência de todos os elementos →
- Configuração eletrônica
- [Xe] 6s2 4f1 5d1
Termodinâmica
- Calor de fusão
- 0,05658911 eV Comparar Calor de fusão de todos os elementos →
- Calor de vaporização
- 3,254392 eV Comparar Calor de vaporização de todos os elementos →
- Calor de sublimação
- 4,124994 eV
- Calor de atomização
- 4,124994 eV
- Entalpia de atomização
- 4,354045 eV
Nuclear
- Prótons
- 58 Comparar Prótons de todos os elementos →
- Nêutrons
- 82 Comparar Nêutrons de todos os elementos →
- Isótopos conhecidos
- 41 Comparar Isótopos conhecidos de todos os elementos →
- Isótopos estáveis
- 1 Comparar Isótopos estáveis de todos os elementos →
- Isótopo mais estável
- Ce-140
- Ano da descoberta
- 1801
Abundância
- Abundância (crosta terrestre)
- 66,5 mg/kg Comparar Abundância (crosta terrestre) de todos os elementos →
- Abundância (oceano)
- 1,2 × 10−6 mg/L Comparar Abundância (oceano) de todos os elementos →
Estrutura cristalina
- Constante de rede a
- 516 pm
Estrutura eletrônica
- Elétrons por camada
- 2, 8, 18, 19, 9, 2 Comparar Elétrons por camada de todos os elementos →
Identificadores
- Número CAS
- 7440-45-1 Comparar Número CAS de todos os elementos →
- Símbolo de termo
- 1G°4
- InChI
- InChI=1S/Ce
- Chave InChI
- GWXLDORMOJMVQZ-UHFFFAOYSA-N
Configuração eletrônica Medido
Ce: 4f¹ 5d¹ 6s²[Xe] 4f¹ 5d¹ 6s²1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹ 5d¹ 6s²Modelo atômico
Os isótopos alteram o número de nêutrons, a massa e a estabilidade — não a configuração eletrônica de um átomo neutro.
Modelo atômico esquemático, sem escala.
Assinatura atômica
Espectro de emissão / absorção
Distribuição isotópica
| Número de massa | Massa atômica (u) | Abundância natural | Meia-vida |
|---|---|---|---|
| 140 Estável | 139,9054431 ± 0,0000023 | 88,4500% | Estável |
Fase / Estado
Motivo: 772,9 °C abaixo do ponto de fusão (797,85 °C)
Esquemático, sem escala
Pontos de transição de fase
Energias de transição
Energia necessária para fundir 1 mol no ponto de fusão
Energia necessária para vaporizar 1 mol no ponto de ebulição
Energia necessária para sublimar 1 mol no ponto de sublimação
Densidade
Em condições padrão
Em condições padrão
Espectros atômicos
Mostrando 10 de 58. Ordenado por carga do íon (ordem crescente).
Dados de linhas disponíveis ?
| Íon | Carga | Total de linhas | Probabilidades de transição | Designações dos níveis |
|---|---|---|---|---|
| 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 |
Dados de níveis disponíveis ?
| Íon | Carga | Níveis |
|---|---|---|
| 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 |
Raios iônicos
| Carga | Coordenação | Spin | Raio |
|---|---|---|---|
| +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 |
Compostos
Isótopos (1)
| Número de massa | Massa atômica (u) | Abundância natural | Meia-vida | Modo de decaimento | |
|---|---|---|---|---|---|
| 140 Estável | 139,9054431 ± 0,0000023 | 88,4500% ± 0,0510% | Estável | stable |
Propriedades ampliadas
Raios covalentes (dados ampliados)
- Raio covalente (Pyykkö)
- 163 pm
- Raio covalente (Pyykkö, ligação dupla)
- 137 pm
- Raio covalente (Pyykkö, ligação tripla)
- 131 pm
Raios de van der Waals
- Alvarez
- 288 pm
- UFF
- 355,6 pm
- MM3
- 274 pm
Raios atômicos e metálicos
- Raio atômico (Rahm)
- 282 pm
Escalas de numeração
- Mendeleev
- 15
- Pettifor
- 32
- Glawe
- 31
Escalas de eletronegatividade
- Ghosh
- 0
- Miedema
- 3
- Gunnarsson–Lundqvist
- 4
- Robles–Bartolotti
- 3
Polarizabilidade e dispersão
- Polarizabilidade dipolar
- 205 a.u.
- Polarizabilidade dipolar (incerteza)
- 20 a.u.
- C₆ (Gould–Bučko)
- 3480 Ha·Bohr6
Parâmetros de Miedema
- Volume molar de Miedema
- 21,62 cm3/mol
- Densidade eletrônica de Miedema
- 2
Risco de abastecimento e economia
- Concentração da produção
- 97
- Risco relativo de abastecimento
- 10
- Distribuição das reservas
- 50
- Estabilidade política (maior produtor)
- 24
- Estabilidade política (detentor das maiores reservas)
- 24
Transições de fase e alótropos
| Ponto de fusão | 1072,15 K |
| Ponto de ebulição | 3716,15 K |
Categorias de estados de oxidação
Dados de referência avançados
Constantes de blindagem (13)
| n | Orbital | 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 |
Detalhes dos raios cristalinos (10)
| Carga | CN | Spin | rcrystal (pm) | Origem |
|---|---|---|---|---|
| 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 |
Modos de decaimento dos isótopos (54)
| Isótopo | Modo | Intensidade |
|---|---|---|
| 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 | — |
Fatores de espalhamento de raios 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 |
Dados adicionais
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
6.65×101 milligrams per kilogram
Referências (1)
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
1.2×10-6 milligrams per liter
Referências (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.
Referências (1)
- [6] Cerium https://periodic.lanl.gov/58.shtml
Referências
(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.