Lanthanum (La)
lanthanideSolid
Peso atômico padrão
138,90547 uConfiguração eletrônica
[Xe] 6s2 5d1Ponto de fusão
917,85 °CPonto de ebulição
3463,85 °CDensidade
6150 kg/m³Estados de oxidação
0, +1, +2, +3Eletronegatividade (Pauling)
1,1Energia de ionização (1ª)
5,5769 eVAno da descoberta
1839Raio atômico
195 pmDetalhes
Lanthanum is the first element of the lanthanide series by common convention, although its 4f shell is empty in the neutral atom. It is a soft, reactive rare-earth metal that occurs with other light rare earths in minerals such as monazite and bastnäsite. Its chemistry is dominated by the large La³⁺ ion, which gives mostly colorless, strongly ionic compounds. Lanthanum is important in optical glass, catalysts, battery alloys, and high-temperature ceramic materials.
Lanthanum is silvery white, malleable, ductile, and soft enough to be cut with a knife. It is one of the most reactive of the rare-earth metals. It oxidizes rapidly when exposed to air. Cold water attacks lanthanum slowly, while hot water attacks it much more rapidly.
The metal reacts directly with elemental carbon, nitrogen, boron, selenium, silicon, phosphorus, sulfur, and with halogens.
At 310°C, lanthanum changes from a hexagonal to a face-centered cubic structure, and at 865°C it again transforms into a body-centered cubic structure.
The name derives from the Greek lanthanein for "to be hidden" or "to escape notice" because it hid in cerium ore and was difficult to separate from that rare earth mineral. Lanthanum was discovered by the Swedish surgeon and chemist Carl-Gustav Mosander in 1839. In 1842, Mosander separated his lanthanium sample into two oxides; for one of these he retained the name lanthanum and for the other he gave the name didymium (or twin).
Lanthanum was discovered by Carl Gustaf Mosander, a Swedish chemist, in 1839. Mosander was searching for impurities he believed existed within samples of cerium. He treated cerium nitrate (Ce(NO3)3) with dilute nitric acid (HNO3) and found a new substance he named lanthana (La2O3). Roughly 0.0018% of the earth's crust is composed of lanthanum. Today, lanthanum is primarily obtained through an ion exchange process from monazite sand ((Ce, La, Th, Nd, Y)PO4), a material rich in rare earth elements that can contain as much as 25% lanthanum.
From the Greek word lanthanein, to escape notice. Mosander in 1839 extracted lanthana from impure cerium nitrate and recognized the new element.
Lanthanum was isolated in relatively pure form in 1923. Iron exchange and solvent extraction techniques have led to much easier isolation of the so-called "rare-earth" elements.
Pure lanthanum is a silvery-white, soft metal that can be cut with a knife when freshly prepared. It tarnishes rapidly in air, forming oxide and hydroxide films, and reacts slowly with cold water but more rapidly when finely divided or heated.
Lanthanum is used in high-refractive-index optical glasses for camera lenses, microscopes, and other precision optics. Mixed rare-earth metal rich in lanthanum has been used in lighter flints and spark-producing alloys. Lanthanum-containing nickel-metal hydride battery alloys store hydrogen reversibly. Lanthanum compounds are also used in fluid catalytic cracking catalysts, ceramic capacitors and dielectric materials, phosphors, and as additives in tungsten electrodes and specialty steels.
Lanthanum 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. Lanthanum also makes up about 25% of Misch metal, a material that is used to make flints for lighters. Lanthana (La2O3) is used to make the glass used in camera lenses and in other special glasses.
Rare-earth compounds containing lanthanum are extensively used in carbon lighting applications, especially by the motion picture industry for studio lighting and projection. This application consumes about 25 percent of the rare-earth compounds produced. La2O3 improves the alkali resistance of glass, and is used in making special optical glasses. Small amounts of lanthanum, as an additive, can be used to produce nodular cast iron.
There is current interest in hydrogen sponge alloys containing lanthanum. These alloys take up to 400 times their own volume of hydrogen gas, and the process is reversible. Every time they take up the gas, heat energy is released; therefore these alloys have possibilities in an energy conservation system.
Isotopes in Earth/Planetary Science
Studies have shown that 138La (with a half-life of 1.06×1011 years) can be used along with 138Ce and 136Ce to measure time elapsed from a supernova explosion producing large numbers of neutrinos [415] T. Hayakawa, T. Shizuma, T. Kajino, K. Ogawa, H. Nakada. Am. Phys. Soc.77, (2008)..
Isotopes in Geochronology
138La decays to 138Ce and 138Ba, respectively, by beta decay with a half-life of 1.06×1011 years and by electron capture with a half-life of 1.56×1011 years. The isotope-amount ratio n(138Ce)/n(142Ce) has been used for dating rocks on long time scales (billions of years) and as a chemical tracer in geochemistry [416] T. Hayashi, M. Tanimizu, T. Tanaka. Precambrian Res.135, 345 (2004).. The increase in radiogenic 138Ba in rocks enriched in rare earth elements, such as allanite, enables one to determine the age of such rocks (Fig. IUPAC.57.1) [417] S. Nakai, H. Shimizu, A. Masuda. Nature320, 433 (1986)..
Isotopes Used as a Source of Radioactive Isotope(s)
139La is used for the production of the medical radioisotope 139Ce via the 139La (p, n) 139Ce reaction [418] H. Aglan, S. A. Kandil, H. A. Hanafi, M. A. Mousa, Z. A. Saleh. J. Radioanal. Nucl. Chem.280, 533 (2009)..
Lanthanum almost exclusively forms compounds in the +3 oxidation state. Lanthanum oxide (La₂O₃) is a basic oxide used in optical glass and ceramics and readily absorbs moisture and CO₂ from air. Lanthanum chloride (LaCl₃), lanthanum nitrate (La(NO₃)₃), and lanthanum carbonate (La₂(CO₃)₃) are common salts of the La³⁺ ion. Lanthanum hexaboride (LaB₆) is a refractory conductor valued as an electron-emission material. Lanthanum strontium manganite, often written La₁₋ₓSrₓMnO₃, is important in oxide electronics and solid oxide fuel-cell cathodes.
See more information at the Lanthanum compound page.
Metallic lanthanum dust and turnings are flammable, and the metal reacts with moisture to release hydrogen. Soluble lanthanum salts can irritate skin, eyes, and the respiratory tract and may disturb calcium-related biological processes at sufficient exposure. Lanthanum has no established essential biological role. Natural lanthanum is effectively stable; radiological risk normally comes from associated thorium or uranium in ores, not from lanthanum itself.
Lanthanum and its compounds have a low to moderate acute toxicity rating; therefore, care should be taken in handling them.
Lanthanum occurs dispersed in the crust with other rare-earth elements and is concentrated mainly in phosphate and carbonate minerals. Weathering releases La³⁺ into soils and waters, where it tends to bind strongly to clays, organic matter, phosphates, and carbonates rather than remain highly mobile. Mining and processing can increase local rare-earth, acid, fluoride, and radionuclide burdens, depending on ore type and waste management.
Lanthanum is obtained chiefly as a co-product of rare-earth mining and separation, especially from bastnäsite and monazite concentrates. Separation relies on solvent extraction or ion-exchange processes because neighboring rare earths have very similar chemistry. It is one of the more abundant and lower-cost rare earths, but supply depends on integrated rare-earth processing capacity and demand for other elements in the same ores. Recycling occurs in limited streams such as nickel-metal hydride batteries and some catalysts, while optical glass and ceramics are less commonly recovered for lanthanum content.
Lanthanum is found in rare-earth minerals such as cerite, monazite, allanite, and bastnasite. Monazite and bastnasite are principal ores in which lanthanum occurs in percentages up to 25 percent and 38 percent respectively. Misch metal, used in making lighter flints, contains about 25 percent lanthanum.
The availability of lanthanum and other rare earths has improved greatly in recent years. The metal can be produced by reducing the anhydrous fluoride with calcium.
Lanthanum is an odd-atomic-number heavy element made mainly by neutron-capture processes followed by radioactive decay in earlier generations of stars. It is far less abundant cosmically than iron-group elements but is measurable in the Sun, meteorites, and many old stars. Its abundance pattern helps distinguish slow and rapid neutron-capture contributions in stellar material.
- Lanthanum metal expands when it solidifies, an uncommon behavior among metals.
- The name comes from Greek lanthanein, meaning to lie hidden, because it was found concealed in cerium minerals.
- La³⁺ is diamagnetic because it has no 4f electrons.
- Lanthanum hexaboride cathodes can emit electrons efficiently at high temperature.
- Lanthanum carbonate is used as a phosphate binder in some medical applications.
Imagens
Propriedades
Física
- Raio atômico (empírico)
- 195 pm Comparar Raio atômico (empírico) de todos os elementos →
- Raio covalente
- 207 pm Comparar Raio covalente de todos os elementos →
- Raio de van der Waals
- 240 pm Comparar Raio de van der Waals de todos os elementos →
- Raio metálico
- 169 pm Comparar Raio metálico de todos os elementos →
- Densidade
- 6150 kg/m³ Comparar Densidade de todos os elementos →
- Volume molar
- 0,0225 L/mol
- Fase nas CNTP
- Sólido Comparar Fase nas CNTP de todos os elementos →
- Ponto de fusão
- 917,85 °C Comparar Ponto de fusão de todos os elementos →
- Ponto de ebulição
- 3463,85 °C Comparar Ponto de ebulição de todos os elementos →
- Condutividade térmica
- 13,4 W/(m·K) Comparar Condutividade térmica de todos os elementos →
- Capacidade calorífica específica
- 0,195 J/(g·K) Comparar Capacidade calorífica específica de todos os elementos →
- Capacidade calorífica molar
- 27,11 J/(mol·K) Comparar Capacidade calorífica molar de todos os elementos →
- Estrutura cristalina
- Hexagonal compacta Comparar Estrutura cristalina de todos os elementos →
Química
- Eletronegatividade (Pauling)
- 1,1 Comparar Eletronegatividade (Pauling) de todos os elementos →
- Afinidade eletrônica
- 0,47 eV
- Energia de ionização (1ª)
- 5,5769 eV Comparar Energia de ionização (1ª) de todos os elementos →
- Energia de ionização (2ª)
- 11,184999 eV Comparar Energia de ionização (2ª) de todos os elementos →
- Energia de ionização (3ª)
- 19,177366 eV Comparar Energia de ionização (3ª) de todos os elementos →
- Energia de ionização (4ª)
- 49,950172 eV Comparar Energia de ionização (4ª) de todos os elementos →
- Energia de ionização (5ª)
- 61,600212 eV Comparar Energia de ionização (5ª) de todos os elementos →
- Estados de oxidação
- 0, +1, +2, +3 Comparar Estados de oxidação de todos os elementos →
- Elétrons de valência
- 3 Comparar Elétrons de valência de todos os elementos →
- Configuração eletrônica
- [Xe] 6s2 5d1
Termodinâmica
- Calor de fusão
- 0,06425869 eV Comparar Calor de fusão de todos os elementos →
- Calor de vaporização
- 4,145722 eV Comparar Calor de vaporização de todos os elementos →
- Calor de sublimação
- 4,467016 eV
- Calor de atomização
- 4,467016 eV
- Entalpia de atomização
- 4,467016 eV
Nuclear
- Prótons
- 57 Comparar Prótons de todos os elementos →
- Nêutrons
- 82 Comparar Nêutrons de todos os elementos →
- Isótopos conhecidos
- 42 Comparar Isótopos conhecidos de todos os elementos →
- Isótopos estáveis
- 1 Comparar Isótopos estáveis de todos os elementos →
- Isótopo mais estável
- La-139
- Ano da descoberta
- 1839
Abundância
- Abundância (crosta terrestre)
- 39 mg/kg Comparar Abundância (crosta terrestre) de todos os elementos →
- Abundância (oceano)
- 3,4 × 10−6 mg/L Comparar Abundância (oceano) de todos os elementos →
Estrutura cristalina
- Constante de rede a
- 375 pm
Estrutura eletrônica
- Elétrons por camada
- 2, 8, 18, 18, 9, 2 Comparar Elétrons por camada de todos os elementos →
Identificadores
- Número CAS
- 7439-91-0 Comparar Número CAS de todos os elementos →
- Símbolo de termo
- 2D3/2
- InChI
- InChI=1S/La
- Chave InChI
- FZLIPJUXYLNCLC-UHFFFAOYSA-N
Configuração eletrônica Medido
La: 5d¹ 6s²[Xe] 5d¹ 6s²1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 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 |
|---|---|---|---|
| 139 Estável | 138,9063563 ± 0,0000024 | 99,9112% | Estável |
Fase / Estado
Motivo: 892,9 °C abaixo do ponto de fusão (917,85 °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 57. Ordenado por carga do íon (ordem crescente).
Dados de linhas disponíveis ?
| Íon | Carga | Total de linhas | Probabilidades de transição | Designações dos níveis |
|---|---|---|---|---|
| La I | 0 | 393 | 315 | 393 |
| La II | +1 | 273 | 84 | 273 |
| La III | +2 | 122 | 0 | 0 |
| La IV | +3 | 87 | 0 | 0 |
| La V | +4 | 42 | 0 | 0 |
Dados de níveis disponíveis ?
| Íon | Carga | Níveis |
|---|---|---|
| La I | 0 | 343 |
| La II | +1 | 119 |
| La III | +2 | 42 |
| La IV | +3 | 52 |
| La V | +4 | 37 |
| La VI | +5 | 2 |
| La VII | +6 | 2 |
| La VIII | +7 | 2 |
| La IX | +8 | 2 |
| La X | +9 | 2 |
Raios iônicos
| Carga | Coordenação | Spin | Raio |
|---|---|---|---|
| +3 | 6 | N/D | 103.2 pm |
| +3 | 7 | N/D | 110.00000000000001 pm |
| +3 | 8 | N/D | 115.99999999999999 pm |
| +3 | 9 | N/D | 121.6 pm |
| +3 | 10 | N/D | 127 pm |
| +3 | 12 | N/D | 136 pm |
Compostos
Isótopos (1)
Natural lanthanum is a mixture of two stable isotopes, 138La and 139La. Twenty three other radioactive isotopes are recognized.
| Número de massa | Massa atômica (u) | Abundância natural | Meia-vida | Modo de decaimento | |
|---|---|---|---|---|---|
| 139 Estável | 138,9063563 ± 0,0000024 | 99,9112% ± 0,0007% | Estável | stable |
Propriedades ampliadas
Raios covalentes (dados ampliados)
- Raio covalente (Pyykkö)
- 180 pm
- Raio covalente (Pyykkö, ligação dupla)
- 139 pm
- Raio covalente (Pyykkö, ligação tripla)
- 139 pm
Raios de van der Waals
- Batsanov
- 250 pm
- Alvarez
- 298 pm
- UFF
- 352,2 pm
- MM3
- 278 pm
Raios atômicos e metálicos
- Raio atômico (Rahm)
- 284 pm
- Raio metálico (C12)
- 187 pm
Escalas de numeração
- Mendeleev
- 13
- Pettifor
- 33
- Glawe
- 32
Escalas de eletronegatividade
- Ghosh
- 0
- Miedema
- 3
- Gunnarsson–Lundqvist
- 4
- Robles–Bartolotti
- 3
Polarizabilidade e dispersão
- Polarizabilidade dipolar
- 215 a.u.
- Polarizabilidade dipolar (incerteza)
- 20 a.u.
- C₆ (Gould–Bučko)
- 3730 Ha·Bohr6
Afinidade química
- Afinidade protônica
- 1013 kJ/mol
- Basicidade em fase gasosa
- 991,9 kJ/mol
Parâmetros de Miedema
- Volume molar de Miedema
- 22,55 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 | 1193,15 K |
| Ponto de ebulição | 3737,15 K |
Categorias de estados de oxidação
Dados de referência avançados
Constantes de blindagem (13)
| n | Orbital | σ |
|---|---|---|
| 1 | s | 1,1317 |
| 2 | p | 4,2044 |
| 2 | s | 15,0466 |
| 3 | d | 13,9398 |
| 3 | p | 18,8604 |
| 3 | s | 19,0569 |
| 4 | d | 32,2748 |
| 4 | f | 55,64 |
| 4 | p | 29,2936 |
| 4 | s | 28,2036 |
Detalhes dos raios cristalinos (6)
| Carga | CN | Spin | rcrystal (pm) | Origem |
|---|---|---|---|---|
| 3 | VI | 117,2 | from r^3 vs V plots, | |
| 3 | VII | 124 | ||
| 3 | VIII | 130 | from r^3 vs V plots, | |
| 3 | IX | 135,6 | from r^3 vs V plots, | |
| 3 | X | 141 | ||
| 3 | XII | 150 | calculated, |
Modos de decaimento dos isótopos (64)
| Isótopo | Modo | Intensidade |
|---|---|---|
| 116 | B+ | — |
| 116 | B+p | — |
| 116 | p | — |
| 117 | p | 100% |
| 117 | B+ | — |
| 117 | B+p | — |
| 118 | B+ | — |
| 118 | B+p | — |
| 119 | B+ | — |
| 120 | B+ | 100% |
Fatores de espalhamento de raios X (711)
| Energia (eV) | f₁ | f₂ |
|---|---|---|
| 10 | — | 3,31251 |
| 10,1152 | — | 3,28769 |
| 10,2317 | — | 3,26306 |
| 10,3496 | — | 3,23861 |
| 10,4688 | — | 3,20975 |
| 10,5894 | — | 3,15961 |
| 10,7114 | — | 3,11024 |
| 10,8348 | — | 3,06165 |
| 10,9596 | — | 3,01382 |
| 11,0859 | — | 2,96673 |
Dados adicionais
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
3.9×101 milligrams per kilogram
Referências (1)
- [5] Lanthanum https://education.jlab.org/itselemental/ele057.html
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
3.4×10-6 milligrams per liter
Referências (1)
- [5] Lanthanum https://education.jlab.org/itselemental/ele057.html
Sources
Sources of this element.
Lanthanum is found in rare-earth minerals such as cerite, monazite, allanite, and bastnasite. Monazite and bastnasite are principal ores in which lanthanum occurs in percentages up to 25 percent and 38 percent respectively. Misch metal, used in making lighter flints, contains about 25 percent lanthanum.
The availability of lanthanum and other rare earths has improved greatly in recent years. The metal can be produced by reducing the anhydrous fluoride with calcium.
Referências (1)
- [6] Lanthanum https://periodic.lanl.gov/57.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 Lanthanum.
The element property data was retrieved from publications.