Astatine (At)
halogenSolid
Peso atomico standard
[210]Configurazione elettronica
[Xe] 6s2 4f14 5d10 6p5Punto di fusione
301,85 °CPunto di ebollizione
N/DDensità
7000 kg/m³Stati di ossidazione
−1, +1, +3, +5, +7Elettronegatività (Pauling)
2,2Energia di ionizzazione (1ª)
9,31751 eVAnno della scoperta
1940Raggio atomico
N/DDettagli
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.
Immagini
Proprietà
Fisiche
- Raggio covalente
- 150 pm Confronta Raggio covalente di tutti gli elementi →
- Raggio di van der Waals
- 202 pm Confronta Raggio di van der Waals di tutti gli elementi →
- Densità
- 7000 kg/m³ Confronta Densità di tutti gli elementi →
- Fase in condizioni STP
- Solido Confronta Fase in condizioni STP di tutti gli elementi →
- Punto di fusione
- 301,85 °C Confronta Punto di fusione di tutti gli elementi →
Chimiche
- Elettronegatività (Pauling)
- 2,2 Confronta Elettronegatività (Pauling) di tutti gli elementi →
- Elettronegatività (Allen)
- 2,39
- Affinità elettronica
- 2,391 eV
- Energia di ionizzazione (1ª)
- 9,31751 eV Confronta Energia di ionizzazione (1ª) di tutti gli elementi →
- Energia di ionizzazione (2ª)
- 17,880062 eV Confronta Energia di ionizzazione (2ª) di tutti gli elementi →
- Energia di ionizzazione (3ª)
- 26,580091 eV Confronta Energia di ionizzazione (3ª) di tutti gli elementi →
- Energia di ionizzazione (4ª)
- 39,650136 eV Confronta Energia di ionizzazione (4ª) di tutti gli elementi →
- Energia di ionizzazione (5ª)
- 50,390173 eV Confronta Energia di ionizzazione (5ª) di tutti gli elementi →
- Stati di ossidazione
- −1, +1, +3, +5, +7 Confronta Stati di ossidazione di tutti gli elementi →
- Elettroni di valenza
- 7 Confronta Elettroni di valenza di tutti gli elementi →
- Configurazione elettronica
- [Xe] 6s2 4f14 5d10 6p5
Termodinamiche
- Calore di fusione
- 0,06218583 eV Confronta Calore di fusione di tutti gli elementi →
- Calore di vaporizzazione
- 0,41457221 eV Confronta Calore di vaporizzazione di tutti gli elementi →
- Calore di sublimazione
- 1,554646 eV
- Calore di atomizzazione
- 1,554646 eV
Nucleari
- Protoni
- 85 Confronta Protoni di tutti gli elementi →
- Neutroni
- 125 Confronta Neutroni di tutti gli elementi →
- Isotopi noti
- 39 Confronta Isotopi noti di tutti gli elementi →
- Isotopi stabili
- 0 Confronta Isotopi stabili di tutti gli elementi →
- Numero di massa (isotopo più stabile)
- 210
- Isotopo più stabile
- At-210
- Anno della scoperta
- 1940
Abbondanza
N/D
Struttura cristallina
N/D
Struttura elettronica
- Elettroni per guscio
- 2, 8, 18, 32, 18, 7 Confronta Elettroni per guscio di tutti gli elementi →
Identificativi
- Numero CAS
- 7440-68-8 Confronta Numero CAS di tutti gli elementi →
- Simbolo di termine
- 2P°3/2
- InChI
- InChI=1S/At
- Chiave InChI
- RYXHOMYVWAEKHL-UHFFFAOYSA-N
Configurazione elettronica Misurato
At: 4f¹⁴ 5d¹⁰ 6s² 6p⁵[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁵Modello atomico
Gli isotopi modificano il numero di neutroni, la massa e la stabilità — non la configurazione elettronica di un atomo neutro.
Modello atomico schematico, non in scala.
Impronta atomica
Spettro di emissione / assorbimento
Distribuzione isotopica
Nessun isotopo stabile.
| Numero di massa | Massa atomica (u) | Abbondanza naturale | Emivita |
|---|---|---|---|
| 214 Radioattivo | 213,9963721 ± 0,0000046 | N/D | 558 ns |
| 197 Radioattivo | 196,993189 ± 0,000055 | N/D | 388.2 ms |
| 196 Radioattivo | 195,9958 ± 0,000033 | N/D | 377 ms |
| 212 Radioattivo | 211,9907377 ± 0,0000026 | N/D | 314 ms |
| 216 Radioattivo | 216,0024236 ± 0,0000039 | N/D | 300 us |
Fase / Stato
Motivo: 276,9 °C sotto il punto di fusione (301,85 °C)
Schema non in scala
Punti di transizione di fase
Energie di transizione
Energia necessaria per fondere 1 mol al punto di fusione
Energia necessaria per vaporizzare 1 mol al punto di ebollizione
Energia necessaria per sublimare 1 mol al punto di sublimazione
Densità
In condizioni standard
In condizioni standard
Spettri atomici
Sono visualizzati 10 di 85. Ordinamento per carica ionica crescente.
Righe disponibili ?
| Ione | Carica | Righe totali | Probabilità di transizione | Designazioni dei livelli |
|---|---|---|---|---|
| At I | 0 | 2 | 0 | 2 |
Livelli disponibili ?
| Ione | Carica | Livelli |
|---|---|---|
| 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 |
Dati sulla struttura cristallina non disponibili
Raggi ionici
| Carica | Coordinazione | Spin | Raggio |
|---|---|---|---|
| +7 | 6 | N/D | 62 pm |
Composti
Isotopi (5)
| Numero di massa | Massa atomica (u) | Abbondanza naturale | Emivita | Modalità di decadimento | |
|---|---|---|---|---|---|
| 214 Radioattivo | 213,9963721 ± 0,0000046 | N/D | 558 ns | α =100% | |
| 197 Radioattivo | 196,993189 ± 0,000055 | N/D | 388.2 ms | α =96.1±1.2%β+ =3.9±1.2% | |
| 196 Radioattivo | 195,9958 ± 0,000033 | N/D | 377 ms | α =97.5±0.3%β+ ?β+SF =0.009±0.1% | |
| 212 Radioattivo | 211,9907377 ± 0,0000026 | N/D | 314 ms | α ≈100%β+ ?β- ? | |
| 216 Radioattivo | 216,0024236 ± 0,0000039 | N/D | 300 us | α ≈100%β- ?ε ? |
Proprietà estese
Raggi covalenti (dati estesi)
- Raggio covalente (Pyykkö)
- 147 pm
- Raggio covalente (Pyykkö, legame doppio)
- 138 pm
- Raggio covalente (Pyykkö, legame triplo)
- 138 pm
Raggi di van der Waals
- Truhlar
- 202 pm
- UFF
- 475 pm
- MM3
- 251 pm
Raggi atomici e metallici
- Raggio atomico (Rahm)
- 247 pm
Scale di numerazione
- Mendeleev
- 110
- Pettifor
- 96
- Glawe
- 98
Scale di elettronegatività
- Ghosh
- 0
- Gunnarsson–Lundqvist
- 7
- Robles–Bartolotti
- 6
Polarizzabilità e dispersione
- Polarizzabilità dipolare
- 42 a.u.
- Polarizzabilità dipolare (inc.)
- 4 a.u.
- C₆ (Gould–Bučko)
- 351 Ha·Bohr6
Transizioni di fase e allotropi
| Punto di fusione | 575,15 K |
Categorie degli stati di ossidazione
Dati di riferimento avanzati
Costanti di schermaggio (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 |
Dettaglio dei raggi cristallini (1)
| Carica | CN | Spin | rcrystal (pm) | Origine |
|---|---|---|---|---|
| 7 | VI | 76 | Ahrens (1952) ionic radius, |
Modalità di decadimento degli isotopi (76)
| Isotopo | Modalità | Intensità |
|---|---|---|
| 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% |
Fattori di diffusione dei raggi 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 |
Dati aggiuntivi
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
Not Applicable
Riferimenti (1)
- [5] Astatine https://education.jlab.org/itselemental/ele085.html
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
Not Applicable
Riferimenti (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.
Riferimenti (1)
- [6] Astatine https://periodic.lanl.gov/85.shtml
Riferimenti
(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.