Astatine (At)
halogenSolid
標準原子量
[210]電子配置
[Xe] 6s2 4f14 5d10 6p5融点
301.85 °C沸点
データなし密度
7000 kg/m³酸化数
−1, +1, +3, +5, +7電気陰性度（Pauling）
2.2第1イオン化エネルギー
9.31751 eV発見年
1940原子半径
データなし詳細
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.
画像
性質
物理的性質
- 共有結合半径
- 150 pm 全元素の共有結合半径を比較 →
- ファンデルワールス半径
- 202 pm 全元素のファンデルワールス半径を比較 →
- 密度
- 7000 kg/m³ 全元素の密度を比較 →
- 標準温度・圧力（STP）での相
- 固体 全元素の標準温度・圧力（STP）での相を比較 →
- 融点
- 301.85 °C 全元素の融点を比較 →
化学的性質
- 電気陰性度（Pauling）
- 2.2 全元素の電気陰性度（Pauling）を比較 →
- 電気陰性度（Allen）
- 2.39
- 電子親和力
- 2.391 eV
- 第1イオン化エネルギー
- 9.31751 eV 全元素の第1イオン化エネルギーを比較 →
- 第2イオン化エネルギー
- 17.880062 eV 全元素の第2イオン化エネルギーを比較 →
- 第3イオン化エネルギー
- 26.580091 eV 全元素の第3イオン化エネルギーを比較 →
- 第4イオン化エネルギー
- 39.650136 eV 全元素の第4イオン化エネルギーを比較 →
- 第5イオン化エネルギー
- 50.390173 eV 全元素の第5イオン化エネルギーを比較 →
- 酸化数
- −1, +1, +3, +5, +7 全元素の酸化数を比較 →
- 価電子
- 7 全元素の価電子を比較 →
- 電子配置
- [Xe] 6s2 4f14 5d10 6p5
熱力学的性質
- 融解熱
- 0.06218583 eV 全元素の融解熱を比較 →
- 蒸発熱
- 0.41457221 eV 全元素の蒸発熱を比較 →
- 昇華熱
- 1.554646 eV
- 原子化熱
- 1.554646 eV
原子核
- 陽子数
- 85 全元素の陽子数を比較 →
- 中性子数
- 125 全元素の中性子数を比較 →
- 既知の同位体
- 39 全元素の既知の同位体を比較 →
- 安定同位体
- 0 全元素の安定同位体を比較 →
- 質量数（最も安定な同位体）
- 210
- 最も安定な同位体
- At-210
- 発見年
- 1940
存在度
データなし
結晶構造
データなし
電子構造
- 各電子殻の電子数
- 2, 8, 18, 32, 18, 7 全元素の各電子殻の電子数を比較 →
識別子
- CAS登録番号
- 7440-68-8 全元素のCAS登録番号を比較 →
- 項記号
- 2P°3/2
- InChI
- InChI=1S/At
- InChI Key
- RYXHOMYVWAEKHL-UHFFFAOYSA-N
電子配置 測定値
At: 4f¹⁴ 5d¹⁰ 6s² 6p⁵[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁵原子モデル
同位体によって中性子数、質量、安定性は変わりますが、中性原子の電子配置は変わりません。
模式的な原子モデルです。実際の縮尺とは異なります。
原子の指紋
発光／吸収スペクトル
同位体分布
安定同位体はありません。
| 質量数 | 原子質量（u） | 天然存在比 | 半減期 |
|---|---|---|---|
| 214 放射性 | 213.9963721 ± 0.0000046 | データなし | 558 ns |
| 197 放射性 | 196.993189 ± 0.000055 | データなし | 388.2 ms |
| 196 放射性 | 195.9958 ± 0.000033 | データなし | 377 ms |
| 212 放射性 | 211.9907377 ± 0.0000026 | データなし | 314 ms |
| 216 放射性 | 216.0024236 ± 0.0000039 | データなし | 300 us |
相／状態
理由: 融点（301.85 °C）より276.9 °C低い
模式図、実際の縮尺とは異なります
相転移点
相転移エネルギー
融点で1 molを融解させるのに必要なエネルギー
沸点で1 molを蒸発させるのに必要なエネルギー
昇華点で1 molを昇華させるのに必要なエネルギー
密度
標準条件下
標準条件下
原子スペクトル
全85件中10件を表示しています。 イオンの電荷の昇順で並べています。
準位データの収録状況 ?
| イオン | 電荷 | 準位 |
|---|---|---|
| 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 |
結晶構造のデータはありません
イオン半径
| 電荷 | 配位 | スピン | 半径 |
|---|---|---|---|
| +7 | 6 | データなし | 62 pm |
化合物
同位体 (5)
| 質量数 | 原子質量（u） | 天然存在比 | 半減期 | 崩壊形式 | |
|---|---|---|---|---|---|
| 214 放射性 | 213.9963721 ± 0.0000046 | データなし | 558 ns | α =100% | |
| 197 放射性 | 196.993189 ± 0.000055 | データなし | 388.2 ms | α =96.1±1.2%β+ =3.9±1.2% | |
| 196 放射性 | 195.9958 ± 0.000033 | データなし | 377 ms | α =97.5±0.3%β+ ?β+SF =0.009±0.1% | |
| 212 放射性 | 211.9907377 ± 0.0000026 | データなし | 314 ms | α ≈100%β+ ?β- ? | |
| 216 放射性 | 216.0024236 ± 0.0000039 | データなし | 300 us | α ≈100%β- ?ε ? |
詳細な性質
共有結合半径（詳細）
- 共有結合半径（Pyykkö）
- 147 pm
- 共有結合半径（Pyykkö、二重結合）
- 138 pm
- 共有結合半径（Pyykkö、三重結合）
- 138 pm
ファンデルワールス半径
- Truhlar
- 202 pm
- UFF
- 475 pm
- MM3
- 251 pm
原子半径と金属半径
- 原子半径（Rahm）
- 247 pm
番号付けの尺度
- Mendeleev
- 110
- Pettifor
- 96
- Glawe
- 98
電気陰性度の尺度
- Ghosh
- 0
- Gunnarsson–Lundqvist
- 7
- Robles–Bartolotti
- 6
分極率と分散
- 双極子分極率
- 42 a.u.
- 双極子分極率（不確かさ）
- 4 a.u.
- C₆ (Gould–Bučko)
- 351 Ha·Bohr6
相転移と同素体
| 融点 | 575.15 K |
酸化数の分類
専門参考データ
遮蔽定数 (15)
| n | 軌道 | 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 |
結晶半径の詳細 (1)
| 電荷 | CN | スピン | rcrystal (pm) | 由来 |
|---|---|---|---|---|
| 7 | VI | 76 | Ahrens (1952) ionic radius, |
同位体の崩壊形式 (76)
| 同位体 | モード | 強度 |
|---|---|---|
| 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% |
X線散乱因子 (516)
| エネルギー (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 |
追加データ
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
Not Applicable
参考文献 (1)
- [5] Astatine https://education.jlab.org/itselemental/ele085.html
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
Not Applicable
参考文献 (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.
参考文献 (1)
- [6] Astatine https://periodic.lanl.gov/85.shtml
参考文献
(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.