Astatine (At)
halogenSolid
Peso atômico padrão
[210]Configuração eletrônica
[Xe] 6s2 4f14 5d10 6p5Ponto de fusão
301,85 °CPonto de ebulição
N/DDensidade
7000 kg/m³Estados de oxidação
−1, +1, +3, +5, +7Eletronegatividade (Pauling)
2,2Energia de ionização (1ª)
9,31751 eVAno da descoberta
1940Raio atômico
N/DDetalhes
Astatine is a very rare, highly radioactive halogen below iodine in group 17. All of its isotopes are unstable, and only minute amounts occur naturally as short-lived products in uranium and thorium decay chains. Its chemistry is partly experimental and partly inferred from periodic trends, because usable quantities are extremely small. Astatine shows both halogen-like behavior and unusually metallic character for a halogen.
The "time of flight" mass spectrometer has been used to confirm that this highly radioactive halogen behaves chemically very much like other halogens, particularly iodine. Astatine is said to be more metallic than iodine, and, like iodine, it probably accumulates in the thyroid gland. Workers at the Brookhaven National Laboratory have recently used reactive scattering in crossed molecular beams to identify and measure elementary reactions involving astatine.
Astatine was produced by Dale R. Carson, K.R. MacKenzie and Emilio Segrè by bombarding an isotope of bismuth, bismuth-209, with alpha particles that had been accelerated in a device called a cyclotron. This created astatine-211 and two free neutrons. This work was conducted at the University of California in 1940. Small amounts of astatine exist in nature as a result of the decay of uranium and thorium, although the total amount of astatine in the earth's crust at any particular time is less than 30 grams. Due to its scarcity, astatine is produced when it is needed. A total of 0.05 micrograms (0.00000005 grams) of astatine have been produced to date.
Astatine's most stable isotope, astatine-210, has a half-life of 8.1 hours. It decays into bismuth-206 through alpha decay or into polonium-210 through electron capture.
From the Greek astatos meaning unstable. Synthesized in 1940 by D.R. Corson, K.R. MacKenzie, and E. Segre at the University of California by bombarding bismuth with alpha particles. The longest-lived isotopes, with naturally occurring uranium and thorium isotopes, and traces of 217At are equilibrium with 233U and 239Np resulting from integration of thorium and uranium with naturally produced neutrons. The total amount of astatine present in the earth's crust, however, is less than 1 oz.
The bulk appearance of astatine has not been directly observed in a macroscopic sample. It is usually handled atom-by-atom or in ultratrace solution. A dark solid, possibly with metallic character, is predicted from periodic trends but is not an experimentally established description.
Astatine has no commercial use as an element. Its main practical interest is in nuclear medicine research, especially ²¹¹At for targeted alpha-particle therapy studies. This isotope can be attached to carrier molecules that seek selected biological targets, but its short half-life and difficult production limit routine use. Other uses are confined to radiochemical research, tracer-scale studies of heavy halogen chemistry, and isotope-production development.
Due to the small amounts produced and its short half-life, there are currently no uses for astatine outside of basic scientific research.
Isotopes in Medicine
211At (with a half-life of 7.2 h) is known to accumulate in the thyroid and occasionally is the preferred treatment for hyperthyroidism and thyroid cancer because the particles emitted from 211At provide more energy than radiolabeled iodine, the other treatment method (Fig. IUPAC.85.1). However, astatine has shown a tendency to induce tumors, so its use is limited [565] L. M. Cobb, A. Harrison, N. E. Dudley, T. E. F. Carr, J. A. Humphreys. Radiother. Oncol.13, 203 (1988).. The 211At-labeled di-carborane (cluster of boron, carbon, and hydrogen atoms) ligand known as the Venus Flytrap Cluster (VFC) has been used as a robust pharmaceutical in radiotherapy treatment [566] J. T. Gullon. “The preparation of metallocarborane and iodinated carborane amino acid analogues for molecular imaging and therapy”, S. dissertation, Dept. of Chemistry, McMaster University, Hamilton, Ontario, Canada (2010). http://hdl.handle.net/11375/9362..
Astatine chemistry is dominated by tracer-scale studies, so many compounds are identified by behavior rather than by isolating bulk material. It can form astatide ions, At⁻, and interhalogen or pseudohalogen-like species. Oxidation states from −1 to positive states such as +1, +3, +5, and possibly +7 are discussed, depending strongly on medium and ligand. Species such as hydrogen astatide, HAt, and astatine monoiodide, AtI, are known or inferred in small-scale studies. Organ astatine compounds with carbon–astatine bonds are important in radiolabeling research.
See more information at the Astatine compound page.
Astatine hazards are dominated by radioactivity, not ordinary chemical toxicity data. Isotope-specific half-lives and decay modes matter; ²¹¹At is an alpha emitter, while other isotopes may have different radiation signatures. Even tiny masses can require shielding, containment, remote handling, and contamination control. Chemical toxicity is poorly characterized because quantities are far below conventional toxicological testing levels.
Natural astatine exists only transiently in trace quantities within radioactive decay chains, mainly associated with uranium- and thorium-bearing minerals. Its atoms decay before they can accumulate or take part in a substantial geochemical cycle. Environmental behavior is therefore inferred from halogen chemistry and radiochemical experiments rather than observed at bulk scale. Releases of artificial astatine would be controlled primarily by its short-lived radioactivity and chemical form.
Astatine has no commodity market and is not mined as a product. Research quantities, especially ²¹¹At, are produced in particle accelerators, commonly by bombarding bismuth targets and then rapidly separating the product. Supply is constrained by isotope half-life, specialized cyclotron access, target processing, transport time, and radiochemical infrastructure. Recycling is not meaningful in the usual industrial sense because the isotopes decay quickly and are used in tracer or medical-research amounts.
Does not occur in nature. Similar to iodine. Produced by bombarding bismuth with alpha particles.
Astatine is not a significant cosmic reservoir element. Any astatine formed in stellar nucleosynthesis or radioactive decay is short-lived on geological and astronomical timescales, so it does not persist in detectable bulk abundance. In planetary materials it can appear only as a temporary daughter product of heavier radioactive nuclides.
- Astatine is usually studied in quantities far below a visible speck.
- The longest-lived known astatine isotopes still have half-lives of only hours.
- The name comes from a Greek word meaning unstable.
- ²¹¹At is valued in research because alpha particles travel only short distances in tissue.
- Astatine can behave less like a simple halogen than iodine does, especially in positive oxidation states.
Imagens
Propriedades
Física
- Raio covalente
- 150 pm Comparar Raio covalente de todos os elementos →
- Raio de van der Waals
- 202 pm Comparar Raio de van der Waals de todos os elementos →
- Densidade
- 7000 kg/m³ Comparar Densidade de todos os elementos →
- Fase nas CNTP
- Sólido Comparar Fase nas CNTP de todos os elementos →
- Ponto de fusão
- 301,85 °C Comparar Ponto de fusão de todos os elementos →
Química
- Eletronegatividade (Pauling)
- 2,2 Comparar Eletronegatividade (Pauling) de todos os elementos →
- Eletronegatividade (Allen)
- 2,39
- Afinidade eletrônica
- 2,391 eV
- Energia de ionização (1ª)
- 9,31751 eV Comparar Energia de ionização (1ª) de todos os elementos →
- Energia de ionização (2ª)
- 17,880062 eV Comparar Energia de ionização (2ª) de todos os elementos →
- Energia de ionização (3ª)
- 26,580091 eV Comparar Energia de ionização (3ª) de todos os elementos →
- Energia de ionização (4ª)
- 39,650136 eV Comparar Energia de ionização (4ª) de todos os elementos →
- Energia de ionização (5ª)
- 50,390173 eV Comparar Energia de ionização (5ª) de todos os elementos →
- Estados de oxidação
- −1, +1, +3, +5, +7 Comparar Estados de oxidação de todos os elementos →
- Elétrons de valência
- 7 Comparar Elétrons de valência de todos os elementos →
- Configuração eletrônica
- [Xe] 6s2 4f14 5d10 6p5
Termodinâmica
- Calor de fusão
- 0,06218583 eV Comparar Calor de fusão de todos os elementos →
- Calor de vaporização
- 0,41457221 eV Comparar Calor de vaporização de todos os elementos →
- Calor de sublimação
- 1,554646 eV
- Calor de atomização
- 1,554646 eV
Nuclear
- Prótons
- 85 Comparar Prótons de todos os elementos →
- Nêutrons
- 125 Comparar Nêutrons de todos os elementos →
- Isótopos conhecidos
- 39 Comparar Isótopos conhecidos de todos os elementos →
- Isótopos estáveis
- 0 Comparar Isótopos estáveis de todos os elementos →
- Número de massa (mais estável)
- 210
- Isótopo mais estável
- At-210
- Ano da descoberta
- 1940
Abundância
N/D
Estrutura cristalina
N/D
Estrutura eletrônica
- Elétrons por camada
- 2, 8, 18, 32, 18, 7 Comparar Elétrons por camada de todos os elementos →
Identificadores
- Número CAS
- 7440-68-8 Comparar Número CAS de todos os elementos →
- Símbolo de termo
- 2P°3/2
- InChI
- InChI=1S/At
- Chave InChI
- RYXHOMYVWAEKHL-UHFFFAOYSA-N
Configuração eletrônica Medido
At: 4f¹⁴ 5d¹⁰ 6s² 6p⁵[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁵Modelo 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
Sem isótopos estáveis.
| Número de massa | Massa atômica (u) | Abundância natural | Meia-vida |
|---|---|---|---|
| 214 Radioativo | 213,9963721 ± 0,0000046 | N/D | 558 ns |
| 197 Radioativo | 196,993189 ± 0,000055 | N/D | 388.2 ms |
| 196 Radioativo | 195,9958 ± 0,000033 | N/D | 377 ms |
| 212 Radioativo | 211,9907377 ± 0,0000026 | N/D | 314 ms |
| 216 Radioativo | 216,0024236 ± 0,0000039 | N/D | 300 us |
Fase / Estado
Motivo: 276,9 °C abaixo do ponto de fusão (301,85 °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 85. Ordenado por carga do íon (ordem crescente).
Dados de linhas disponíveis ?
| Íon | Carga | Total de linhas | Probabilidades de transição | Designações dos níveis |
|---|---|---|---|---|
| At I | 0 | 2 | 0 | 2 |
Dados de níveis disponíveis ?
| Íon | Carga | Níveis |
|---|---|---|
| At I | 0 | 4 |
| At II | +1 | 2 |
| At III | +2 | 2 |
| At IV | +3 | 2 |
| At V | +4 | 2 |
| At VI | +5 | 2 |
| At VII | +6 | 2 |
| At VIII | +7 | 2 |
| At IX | +8 | 2 |
| At X | +9 | 2 |
Dados de estrutura cristalina indisponíveis
Raios iônicos
| Carga | Coordenação | Spin | Raio |
|---|---|---|---|
| +7 | 6 | N/D | 62 pm |
Compostos
Isótopos (5)
| Número de massa | Massa atômica (u) | Abundância natural | Meia-vida | Modo de decaimento | |
|---|---|---|---|---|---|
| 214 Radioativo | 213,9963721 ± 0,0000046 | N/D | 558 ns | α =100% | |
| 197 Radioativo | 196,993189 ± 0,000055 | N/D | 388.2 ms | α =96.1±1.2%β+ =3.9±1.2% | |
| 196 Radioativo | 195,9958 ± 0,000033 | N/D | 377 ms | α =97.5±0.3%β+ ?β+SF =0.009±0.1% | |
| 212 Radioativo | 211,9907377 ± 0,0000026 | N/D | 314 ms | α ≈100%β+ ?β- ? | |
| 216 Radioativo | 216,0024236 ± 0,0000039 | N/D | 300 us | α ≈100%β- ?ε ? |
Propriedades ampliadas
Raios covalentes (dados ampliados)
- Raio covalente (Pyykkö)
- 147 pm
- Raio covalente (Pyykkö, ligação dupla)
- 138 pm
- Raio covalente (Pyykkö, ligação tripla)
- 138 pm
Raios de van der Waals
- Truhlar
- 202 pm
- UFF
- 475 pm
- MM3
- 251 pm
Raios atômicos e metálicos
- Raio atômico (Rahm)
- 247 pm
Escalas de numeração
- Mendeleev
- 110
- Pettifor
- 96
- Glawe
- 98
Escalas de eletronegatividade
- Ghosh
- 0
- Gunnarsson–Lundqvist
- 7
- Robles–Bartolotti
- 6
Polarizabilidade e dispersão
- Polarizabilidade dipolar
- 42 a.u.
- Polarizabilidade dipolar (incerteza)
- 4 a.u.
- C₆ (Gould–Bučko)
- 351 Ha·Bohr6
Transições de fase e alótropos
| Ponto de fusão | 575,15 K |
Categorias de estados de oxidação
Dados de referência avançados
Constantes de blindagem (15)
| n | Orbital | σ |
|---|---|---|
| 1 | s | 1,6446 |
| 2 | p | 4,5524 |
| 2 | s | 22,3324 |
| 3 | d | 13,4155 |
| 3 | p | 23,5024 |
| 3 | s | 24,6481 |
| 4 | d | 37,9504 |
| 4 | f | 37,7596 |
| 4 | p | 36,516 |
| 4 | s | 35,6644 |
Detalhes dos raios cristalinos (1)
| Carga | CN | Spin | rcrystal (pm) | Origem |
|---|---|---|---|---|
| 7 | VI | 76 | Ahrens (1952) ionic radius, |
Modos de decaimento dos isótopos (76)
| Isótopo | Modo | Intensidade |
|---|---|---|
| 191 | A | 100% |
| 191 | B+ | — |
| 192 | A | 100% |
| 192 | B+ | — |
| 192 | B+SF | 0,5% |
| 193 | A | 100% |
| 194 | A | 100% |
| 194 | B+ | 8,3% |
| 194 | B+SF | 0% |
| 195 | A | 100% |
Fatores de espalhamento de raios X (516)
| Energia (eV) | f₁ | f₂ |
|---|---|---|
| 10 | — | 8,78144 |
| 10,1617 | — | 8,87321 |
| 10,3261 | — | 8,96593 |
| 10,4931 | — | 9,04836 |
| 10,6628 | — | 9,08532 |
| 10,8353 | — | 9,12244 |
| 11,0106 | — | 9,1597 |
| 11,1886 | — | 9,1933 |
| 11,3696 | — | 9,15142 |
| 11,5535 | — | 9,10973 |
Dados adicionais
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
Not Applicable
Referências (1)
- [5] Astatine https://education.jlab.org/itselemental/ele085.html
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
Not Applicable
Referências (1)
- [5] Astatine https://education.jlab.org/itselemental/ele085.html
Production
Production of this element (from raw materials or other compounds containing the element).
Astatine can be produced by bombarding bismuth with energetic alpha particles to obtain the relatively long-lived 209-211At, which can be distilled from the target by heating in air.
Referências (1)
- [6] Astatine https://periodic.lanl.gov/85.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 Astatine.
The element property data was retrieved from publications.