Astatine (At)
halogenSolid
Peso atómico estándar
[210]Configuración electrónica
[Xe] 6s2 4f14 5d10 6p5Punto de fusión
301,85 °CPunto de ebullición
N/DDensidad
7000 kg/m³Estados de oxidación
−1, +1, +3, +5, +7Electronegatividad (Pauling)
2,2Energía de ionización (1.ª)
9,31751 eVAño de descubrimiento
1940Radio atómico
N/DDetalles
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.
Imágenes
Propiedades
Físicas
- Radio covalente
- 150 pm Comparar Radio covalente de todos los elementos →
- Radio de van der Waals
- 202 pm Comparar Radio de van der Waals de todos los elementos →
- Densidad
- 7000 kg/m³ Comparar Densidad de todos los elementos →
- Fase en CNPT
- Sólido Comparar Fase en CNPT de todos los elementos →
- Punto de fusión
- 301,85 °C Comparar Punto de fusión de todos los elementos →
Químicas
- Electronegatividad (Pauling)
- 2,2 Comparar Electronegatividad (Pauling) de todos los elementos →
- Electronegatividad (Allen)
- 2,39
- Afinidad electrónica
- 2,391 eV
- Energía de ionización (1.ª)
- 9,31751 eV Comparar Energía de ionización (1.ª) de todos los elementos →
- Energía de ionización (2.ª)
- 17,880062 eV Comparar Energía de ionización (2.ª) de todos los elementos →
- Energía de ionización (3.ª)
- 26,580091 eV Comparar Energía de ionización (3.ª) de todos los elementos →
- Energía de ionización (4.ª)
- 39,650136 eV Comparar Energía de ionización (4.ª) de todos los elementos →
- Energía de ionización (5.ª)
- 50,390173 eV Comparar Energía de ionización (5.ª) de todos los elementos →
- Estados de oxidación
- −1, +1, +3, +5, +7 Comparar Estados de oxidación de todos los elementos →
- Electrones de valencia
- 7 Comparar Electrones de valencia de todos los elementos →
- Configuración electrónica
- [Xe] 6s2 4f14 5d10 6p5
Termodinámicas
- Calor de fusión
- 0,06218583 eV Comparar Calor de fusión de todos los elementos →
- Calor de vaporización
- 0,41457221 eV Comparar Calor de vaporización de todos los elementos →
- Calor de sublimación
- 1,554646 eV
- Calor de atomización
- 1,554646 eV
Nucleares
- Protones
- 85 Comparar Protones de todos los elementos →
- Neutrones
- 125 Comparar Neutrones de todos los elementos →
- Isótopos conocidos
- 39 Comparar Isótopos conocidos de todos los elementos →
- Isótopos estables
- 0 Comparar Isótopos estables de todos los elementos →
- Número másico (isótopo más estable)
- 210
- Isótopo más estable
- At-210
- Año de descubrimiento
- 1940
Abundancia
N/D
Estructura cristalina
N/D
Estructura electrónica
- Electrones por capa
- 2, 8, 18, 32, 18, 7 Comparar Electrones por capa de todos los elementos →
Identificadores
- Número CAS
- 7440-68-8 Comparar Número CAS de todos los elementos →
- Símbolo del término
- 2P°3/2
- InChI
- InChI=1S/At
- Clave InChI
- RYXHOMYVWAEKHL-UHFFFAOYSA-N
Configuración electrónica 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 atómico
Los isótopos cambian el número de neutrones, la masa y la estabilidad, pero no la configuración electrónica de un átomo neutro.
Modelo atómico esquemático, no a escala.
Huella atómica
Espectro de emisión / absorción
Distribución isotópica
No hay isótopos estables.
| Número másico | Masa atómica (u) | Abundancia natural | Periodo de semidesintegración |
|---|---|---|---|
| 214 Radiactivo | 213,9963721 ± 0,0000046 | N/D | 558 ns |
| 197 Radiactivo | 196,993189 ± 0,000055 | N/D | 388.2 ms |
| 196 Radiactivo | 195,9958 ± 0,000033 | N/D | 377 ms |
| 212 Radiactivo | 211,9907377 ± 0,0000026 | N/D | 314 ms |
| 216 Radiactivo | 216,0024236 ± 0,0000039 | N/D | 300 us |
Fase / Estado
Motivo: 276,9 °C por debajo del punto de fusión (301,85 °C)
Esquemático, no a escala
Puntos de transición de fase
Energías de transición
Energía necesaria para fundir 1 mol en el punto de fusión
Energía necesaria para vaporizar 1 mol en el punto de ebullición
Energía necesaria para sublimar 1 mol en el punto de sublimación
Densidad
En condiciones estándar
En condiciones estándar
Espectros atómicos
Se muestran 10 de 85. Ordenado por carga del ion (ascendente).
Líneas disponibles ?
| Ion | Carga | Total de líneas | Probabilidades de transición | Designaciones de los niveles |
|---|---|---|---|---|
| At I | 0 | 2 | 0 | 2 |
Niveles disponibles ?
| Ion | Carga | Niveles |
|---|---|---|
| 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 |
No hay datos disponibles sobre la estructura cristalina
Radios iónicos
| Carga | Coordinación | Espín | Radio |
|---|---|---|---|
| +7 | 6 | N/D | 62 pm |
Compuestos
Isótopos (5)
| Número másico | Masa atómica (u) | Abundancia natural | Periodo de semidesintegración | Modo de desintegración | |
|---|---|---|---|---|---|
| 214 Radiactivo | 213,9963721 ± 0,0000046 | N/D | 558 ns | α =100% | |
| 197 Radiactivo | 196,993189 ± 0,000055 | N/D | 388.2 ms | α =96.1±1.2%β+ =3.9±1.2% | |
| 196 Radiactivo | 195,9958 ± 0,000033 | N/D | 377 ms | α =97.5±0.3%β+ ?β+SF =0.009±0.1% | |
| 212 Radiactivo | 211,9907377 ± 0,0000026 | N/D | 314 ms | α ≈100%β+ ?β- ? | |
| 216 Radiactivo | 216,0024236 ± 0,0000039 | N/D | 300 us | α ≈100%β- ?ε ? |
Propiedades ampliadas
Radios covalentes (ampliados)
- Radio covalente (Pyykkö)
- 147 pm
- Radio covalente (Pyykkö, enlace doble)
- 138 pm
- Radio covalente (Pyykkö, enlace triple)
- 138 pm
Radios de van der Waals
- Truhlar
- 202 pm
- UFF
- 475 pm
- MM3
- 251 pm
Radios atómicos y metálicos
- Radio atómico (Rahm)
- 247 pm
Escalas de numeración
- Mendeleev
- 110
- Pettifor
- 96
- Glawe
- 98
Escalas de electronegatividad
- Ghosh
- 0
- Gunnarsson–Lundqvist
- 7
- Robles–Bartolotti
- 6
Polarizabilidad y dispersión
- Polarizabilidad dipolar
- 42 a.u.
- Polarizabilidad dipolar (incert.)
- 4 a.u.
- C₆ (Gould–Bučko)
- 351 Ha·Bohr6
Transiciones de fase y alótropos
| Punto de fusión | 575,15 K |
Categorías de estados de oxidación
Datos de referencia avanzados
Constantes de apantallamiento (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 |
Detalle de los radios cristalinos (1)
| Carga | CN | Espín | rcrystal (pm) | Origen |
|---|---|---|---|---|
| 7 | VI | 76 | Ahrens (1952) ionic radius, |
Modos de desintegración de los isótopos (76)
| Isótopo | Modo | Intensidad |
|---|---|---|
| 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% |
Factores de dispersión de rayos X (516)
| Energía (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 |
Datos adicionales
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
Not Applicable
Referencias (1)
- [5] Astatine https://education.jlab.org/itselemental/ele085.html
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
Not Applicable
Referencias (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.
Referencias (1)
- [6] Astatine https://periodic.lanl.gov/85.shtml
Referencias
(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.