Astatine (At)
halogenSolid
Masse atomique relative standard
[210]Configuration électronique
[Xe] 6s2 4f14 5d10 6p5Point de fusion
301,85 °CPoint d’ébullition
N/DMasse volumique
7000 kg/m³États d’oxydation
−1, +1, +3, +5, +7Électronégativité (Pauling)
2,2Énergie d’ionisation (1re)
9,31751 eVAnnée de découverte
1940Rayon atomique
N/DDétails
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.
Images
Propriétés
Propriétés physiques
- Rayon covalent
- 150 pm Comparer : Rayon covalent de tous les éléments →
- Rayon de van der Waals
- 202 pm Comparer : Rayon de van der Waals de tous les éléments →
- Masse volumique
- 7000 kg/m³ Comparer : Masse volumique de tous les éléments →
- Phase aux CNTP
- Solide Comparer : Phase aux CNTP de tous les éléments →
- Point de fusion
- 301,85 °C Comparer : Point de fusion de tous les éléments →
Propriétés chimiques
- Électronégativité (Pauling)
- 2,2 Comparer : Électronégativité (Pauling) de tous les éléments →
- Électronégativité (Allen)
- 2,39
- Affinité électronique
- 2,391 eV
- Énergie d’ionisation (1re)
- 9,31751 eV Comparer : Énergie d’ionisation (1re) de tous les éléments →
- Énergie d’ionisation (2e)
- 17,880062 eV Comparer : Énergie d’ionisation (2e) de tous les éléments →
- Énergie d’ionisation (3e)
- 26,580091 eV Comparer : Énergie d’ionisation (3e) de tous les éléments →
- Énergie d’ionisation (4e)
- 39,650136 eV Comparer : Énergie d’ionisation (4e) de tous les éléments →
- Énergie d’ionisation (5e)
- 50,390173 eV Comparer : Énergie d’ionisation (5e) de tous les éléments →
- États d’oxydation
- −1, +1, +3, +5, +7 Comparer : États d’oxydation de tous les éléments →
- Électrons de valence
- 7 Comparer : Électrons de valence de tous les éléments →
- Configuration électronique
- [Xe] 6s2 4f14 5d10 6p5
Propriétés thermodynamiques
- Enthalpie de fusion
- 0,06218583 eV Comparer : Enthalpie de fusion de tous les éléments →
- Enthalpie de vaporisation
- 0,41457221 eV Comparer : Enthalpie de vaporisation de tous les éléments →
- Enthalpie de sublimation
- 1,554646 eV
- Enthalpie d’atomisation
- 1,554646 eV
Propriétés nucléaires
- Protons
- 85 Comparer : Protons de tous les éléments →
- Neutrons
- 125 Comparer : Neutrons de tous les éléments →
- Isotopes connus
- 39 Comparer : Isotopes connus de tous les éléments →
- Isotopes stables
- 0 Comparer : Isotopes stables de tous les éléments →
- Nombre de masse (isotope le plus stable)
- 210
- Isotope le plus stable
- At-210
- Année de découverte
- 1940
Abondance
N/D
Structure cristalline
N/D
Structure électronique
- Électrons par couche
- 2, 8, 18, 32, 18, 7 Comparer : Électrons par couche de tous les éléments →
Identifiants
- Numéro CAS
- 7440-68-8 Comparer : Numéro CAS de tous les éléments →
- Symbole de terme
- 2P°3/2
- InChI
- InChI=1S/At
- Clé InChI
- RYXHOMYVWAEKHL-UHFFFAOYSA-N
Configuration électronique Mesuré
At: 4f¹⁴ 5d¹⁰ 6s² 6p⁵[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁵Modèle atomique
Les isotopes diffèrent par leur nombre de neutrons, leur masse et leur stabilité — pas par la configuration électronique de l’atome neutre.
Modèle atomique schématique, non à l’échelle.
Empreinte atomique
Spectre d’émission / d’absorption
Distribution isotopique
Aucun isotope stable.
| Nombre de masse | Masse atomique (u) | Abondance naturelle | Demi-vie |
|---|---|---|---|
| 214 Radioactif | 213,9963721 ± 0,0000046 | N/D | 558 ns |
| 197 Radioactif | 196,993189 ± 0,000055 | N/D | 388.2 ms |
| 196 Radioactif | 195,9958 ± 0,000033 | N/D | 377 ms |
| 212 Radioactif | 211,9907377 ± 0,0000026 | N/D | 314 ms |
| 216 Radioactif | 216,0024236 ± 0,0000039 | N/D | 300 us |
Phase / État
Explication: 276,9 °C en dessous du point de fusion (301,85 °C)
Schématique, non à l’échelle
Points de transition de phase
Énergies de transition
Énergie nécessaire pour faire fondre 1 mol au point de fusion
Énergie nécessaire pour vaporiser 1 mol au point d’ébullition
Énergie nécessaire pour sublimer 1 mol au point de sublimation
Masse volumique
Dans les conditions standard
Dans les conditions standard
Spectres atomiques
Affichage de 10 sur 85. Tri par charge ionique croissante.
Raies répertoriées ?
| Ion | Charge | Nombre total de raies | Probabilités de transition | Désignations des niveaux |
|---|---|---|---|---|
| At I | 0 | 2 | 0 | 2 |
Niveaux répertoriés ?
| Ion | Charge | Niveaux |
|---|---|---|
| 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 |
Données de structure cristalline indisponibles
Rayons ioniques
| Charge | Coordinence | Spin | Rayon |
|---|---|---|---|
| +7 | 6 | N/D | 62 pm |
Composés
Isotopes (5)
| Nombre de masse | Masse atomique (u) | Abondance naturelle | Demi-vie | Mode de désintégration | |
|---|---|---|---|---|---|
| 214 Radioactif | 213,9963721 ± 0,0000046 | N/D | 558 ns | α =100% | |
| 197 Radioactif | 196,993189 ± 0,000055 | N/D | 388.2 ms | α =96.1±1.2%β+ =3.9±1.2% | |
| 196 Radioactif | 195,9958 ± 0,000033 | N/D | 377 ms | α =97.5±0.3%β+ ?β+SF =0.009±0.1% | |
| 212 Radioactif | 211,9907377 ± 0,0000026 | N/D | 314 ms | α ≈100%β+ ?β- ? | |
| 216 Radioactif | 216,0024236 ± 0,0000039 | N/D | 300 us | α ≈100%β- ?ε ? |
Propriétés étendues
Rayons covalents (données étendues)
- Rayon covalent (Pyykkö)
- 147 pm
- Rayon covalent (Pyykkö, liaison double)
- 138 pm
- Rayon covalent (Pyykkö, liaison triple)
- 138 pm
Rayons de van der Waals
- Truhlar
- 202 pm
- UFF
- 475 pm
- MM3
- 251 pm
Rayons atomiques et métalliques
- Rayon atomique (Rahm)
- 247 pm
Échelles de numérotation
- Mendeleev
- 110
- Pettifor
- 96
- Glawe
- 98
Échelles d’électronégativité
- Ghosh
- 0
- Gunnarsson–Lundqvist
- 7
- Robles–Bartolotti
- 6
Polarisabilité et dispersion
- Polarisabilité dipolaire
- 42 a.u.
- Polarisabilité dipolaire (incertitude)
- 4 a.u.
- C₆ (Gould–Bučko)
- 351 Ha·Bohr6
Transitions de phase et allotropes
| Point de fusion | 575,15 K |
Catégories d’états d’oxydation
Données de référence avancées
Constantes d’écran (15)
| n | Orbitale | 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 |
Détail des rayons cristallins (1)
| Charge | CN | Spin | rcrystal (pm) | Origine |
|---|---|---|---|---|
| 7 | VI | 76 | Ahrens (1952) ionic radius, |
Modes de désintégration des isotopes (76)
| Isotope | Mode | Intensité |
|---|---|---|
| 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% |
Facteurs de diffusion des rayons X (516)
| Énergie (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 |
Données complémentaires
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
Not Applicable
Références (1)
- [5] Astatine https://education.jlab.org/itselemental/ele085.html
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
Not Applicable
Références (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.
Références (1)
- [6] Astatine https://periodic.lanl.gov/85.shtml
Références
(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.
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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.