Polonium (Po)
metalloidSolid
標準原子量
[209]電子配置
[Xe] 6s2 4f14 5d10 6p4融点
253.85 °C沸点
961.85 °C密度
9320 kg/m³酸化数
−2, +2, +4, +5, +6電気陰性度（Pauling）
2第1イオン化エネルギー
8.41807 eV発見年
1898原子半径
190 pm詳細
Polonium is a very rare, highly radioactive chalcogen below tellurium in group 16. It occurs naturally only in minute amounts as part of uranium and thorium decay chains, chiefly through isotopes such as ²¹⁰Po. Its chemistry combines metallic character with chalcogen behavior, and its significance comes mainly from intense alpha radioactivity rather than from ordinary materials use.
Polonium-210 is a low-melting, fairly volatile metal, 50% of which is vaporized in air in 45 hours at 55°C. It is an alpha emitter with a half-life of 138.39 days. A milligram emits as many alpha particles as 5 g of radium.
The energy released by its decay is so large (140W/g) that a capsule containing about half a gram reaches a temperature above 500C. The capsule also presents a contact gamma-ray dose rate of 0.012 Gy/h. A few curies (1 curie = 3.7 x 1010Bq) of polonium exhibit a blue glow, caused by excitation of the surrounding gas.
Polonium is readily dissolved in dilute acids, but is only slightly soluble in alkali. Polonium salts of organic acids char rapidly; halide amines are reduced to the metal.
Polonium was discovered by Marie Sklodowska Curie, a Polish chemist, in 1898. She obtained polonium from pitchblende, a material that contains uranium, after noticing that unrefined pitchblende was more radioactive than the uranium that was separated from it. She reasoned that pitchblende must contain at least one other radioactive element. Curie needed to refine several tons of pitchblende in order to obtain tiny amounts of polonium and radium, another radioactive element discovered by Curie. One ton of uranium ore contains only about 100 micrograms (0.0001 grams) of polonium. Due to its scarcity, polonium is usually produced by bombarding bismuth-209 with neutrons in a nuclear reactor. This forms bismuth-210, which has a half-life of 5 days. Bismuth-210 decays into polonium-210 through beta decay. Milligram amounts of polonium-210 have been produced by this method.
Polonium-210 is a very strong emitter of alpha particles. A single gram of polonium-210 creates 140 Watts of heat energy and is being considered as a lightweight heat source for thermoelectric power for spacecraft. Polonium-210 has a half-life of 138.39 days.
Polonium's most stable isotope, polonium-209, has a half-life of 102 years. It decays into lead-205 through alpha decay. Polonium-209 is available from Oak Ridge National Laboratory at the cost of about $3200 per microcurie.
Named after Poland, native country of Madam Curie. Polonium, also called Radium F, was the first element discovered by Curie in 1898 while seeking the cause of radioactivity of pitchblend from Joachimsthal, Bohemia. The electroscope showed it separating with bismuth.
Macroscopic polonium is difficult to handle and observe because it self-heats and rapidly accumulates radiation damage. The pure element is reported as a silvery metal; two solid allotropes are known near ordinary temperatures, including a simple cubic form unusual among elements.
Polonium has no broad commercial use. Historically, ²¹⁰Po was used in static eliminators and neutron sources when mixed with beryllium, where alpha particles drive neutron emission. Such uses have largely been replaced or tightly restricted because of radiological risk and regulatory burden. Small quantities remain relevant for calibration, specialized research, and legacy sealed-source applications.
Polonium can be used to eliminate static electricity in machinery that is caused by processes such as the rolling of paper, wire or sheet metal, although other materials which emit beta particles are more commonly used for this purpose. Polonium is also used in brushes for removing dust from photographic films, although the polonium must be carefully sealed to protect the user from contamination. Polonium is also combined with beryllium to form neutron sources.
Because almost all alpha radiation is stopped within the solid source and its container, giving up its energy, polonium has attracted attention for uses as a lightweight heat source for thermoelectric power in space satellites.
Polonium can be mixed or alloyed with beryllium to provide a source of neutrons. The element has been used in devices for eliminating static charges in textile mills, etc.; however, beta sources are both more commonly used and less dangerous. It is also used on brushes for removing dust from photographic films. The polonium for these is carefully sealed and controlled, minimizing hazards to the user.
Isotopes in Industry
210Po (with a half-life of 138 days) is used as static eliminator to remove static electricity in machinery. This is useful in machinery that produces electricity easily, for example, via rolling paper, manufacturing sheet plastics, and spinning synthetic fibers, which all readily produce static [75] J. Peterson, M. McDonell, L. Haroun, F. Monette, R. D. Hildebrand, A. Taboas. Radiological and Chemical Fact Sheets to Support Health Risk Analyses for Contaminated Areas, Prepared by Argonne National Laboratory Environmental Science Division in collaboration with U.S. Department of Energy, Richland Operations Office and Chicago Operations Office (2014), Feb. 22; http://www.remm.nlm.gov/ANL_ContaminantFactSheets_All_070418.pdf., [563] United States Nuclear Regulatory Commission. Backgrounder on Polonium-210, United States Nuclear Regulatory Commission (2017), April 8; http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/polonium.html.. 210Po can also make use of its static eliminating properties when used in brushes that function to clean camera lenses and photographic films (Fig. IUPAC.84.1) [75] J. Peterson, M. McDonell, L. Haroun, F. Monette, R. D. Hildebrand, A. Taboas. Radiological and Chemical Fact Sheets to Support Health Risk Analyses for Contaminated Areas, Prepared by Argonne National Laboratory Environmental Science Division in collaboration with U.S. Department of Energy, Richland Operations Office and Chicago Operations Office (2014), Feb. 22; http://www.remm.nlm.gov/ANL_ContaminantFactSheets_All_070418.pdf.. 210Po has been used to manufacture atomic weapons. When combined with beryllium, polonium can act as a neutron-producing initiator. However, because of its short half-life, 210Po is no longer used in this manner [75] J. Peterson, M. McDonell, L. Haroun, F. Monette, R. D. Hildebrand, A. Taboas. Radiological and Chemical Fact Sheets to Support Health Risk Analyses for Contaminated Areas, Prepared by Argonne National Laboratory Environmental Science Division in collaboration with U.S. Department of Energy, Richland Operations Office and Chicago Operations Office (2014), Feb. 22; http://www.remm.nlm.gov/ANL_ContaminantFactSheets_All_070418.pdf..
Polonium chemistry is best known for oxidation states −2, +2, +4, and +6, with +4 often prominent in aqueous and halide chemistry. Representative compounds include polonium dioxide, PoO₂, polonium tetrachloride, PoCl₄, and polonium hydride, H₂Po, an unstable hydrogen chalcogenide. Polonides are formed with electropositive metals, but many compounds are hard to study because radiolysis and self-heating alter samples.
See more information at the Polonium compound page.
Polonium is an extreme internal radiological hazard, especially ²¹⁰Po, an alpha emitter. Alpha particles are stopped by skin or thin barriers, but inhaled, ingested, or wound-introduced material can deliver severe localized doses. The element is also chemically toxic, though radiation dominates most risk assessments. Work requires sealed containment, contamination control, and isotope-specific monitoring.
Polonium-210 is very dangerous to handle in even milligram or microgram amounts, and special equipment and strict control is necessary. Damage arises from the complete absorption of the energy of the alpha particle into tissue.
Natural polonium is generated continuously in uranium and thorium decay series and is present at trace levels in rocks, soils, seawater, and the atmosphere. ²¹⁰Po can be transferred through air, water, and food webs, often following particles and sulfur- or selenium-like chemical pathways. It decays rather than persisting indefinitely, but local concentrations can matter in biological and radiological studies.
Polonium is not a traded bulk commodity. Usable ²¹⁰Po is produced in specialized nuclear facilities, commonly by neutron irradiation of bismuth to form ²¹⁰Bi, which decays to ²¹⁰Po, followed by radiochemical separation. Supply is limited by short half-life, licensing, security, and handling costs rather than ore availability. Substitution by less hazardous technologies has sharply reduced routine demand, so production is small and purpose-specific.
Polonium is a very rare natural element. Uranium ores contain only about 100 micrograms of the element per ton. Its abundance is only about 0.2% of that of radium.
In 1934, scientists discovered that when they bombarded natural bismuth (209Bi) with neutrons, 210Bi, the parent of polonium, was obtained. Milligram amounts of polonium may now be prepared this way, by using the high neutron fluxes of nuclear reactors.
Polonium has no stable isotopes, so primordial polonium has long since decayed. In space it is expected only as a transient product of radioactive decay chains or nucleosynthesis pathways involving heavy nuclei. Any detectable amount in planetary materials reflects recent generation from longer-lived actinides, not independent cosmic abundance.
- ²¹⁰Po has a half-life of about 138 days, which strongly limits storage and distribution.
- Polonium was identified by Marie and Pierre Curie in pitchblende residues in 1898.
- The name honored Poland, which was not then an independent state.
- Elemental polonium can become warm from its own alpha-decay heat.
- A polonium-beryllium source produces neutrons without requiring a reactor during use.
- Polonium's simple cubic alpha allotrope is rare among elemental crystal structures.
画像
性質
物理的性質
- 原子半径（経験値）
- 190 pm 全元素の原子半径（経験値）を比較 →
- 共有結合半径
- 140 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
- 197 pm 全元素のファンデルワールス半径を比較 →
- 密度
- 9320 kg/m³ 全元素の密度を比較 →
- モル体積
- 0.0227 L/mol
- 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
- 253.85 °C 全元素の融点を比較 →
- 沸点
- 961.85 °C 全元素の沸点を比較 →
- 結晶構造
- 単純立方構造 全元素の結晶構造を比較 →
化学的性質
- 電気陰性度（Pauling）
- 2 全元素の電気陰性度（Pauling）を比較 →
- 電気陰性度（Allen）
- 2.19
- 電子親和力
- 1.9 eV
- 第1イオン化エネルギー
- 8.41807 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
- 19.300066 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
- 27.300094 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
- 36.000124 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
- 57.000196 eV 全元素の第5イオン化エネルギーを比較 →
- 酸化数
- −2, +2, +4, +5, +6 全元素の酸化数を比較 →
- 価電子
- 6 全元素の価電子を比較 →
- 電子配置
- [Xe] 6s2 4f14 5d10 6p4
熱力学的性質
- 融解熱
- 0.13473597 eV 全元素の融解熱を比較 →
- 蒸発熱
- 1.057159 eV 全元素の蒸発熱を比較 →
- 昇華熱
- 1.824118 eV
- 原子化熱
- 1.824118 eV
原子核
- 陽子数
- 84 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
- 42 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）
- 209
- 最も安定な同位体
- Po-209
- 発見年
- 1898
存在度
- 存在度（地殻）
- 2e-10 mg/kg 全元素の存在度（地殻）を比較 →
- 存在度（海洋）
- 1.5 × 10−14 mg/L 全元素の存在度（海洋）を比較 →
結晶構造
- 格子定数a
- 335 pm
電子構造
- 各電子殻の電子数
- 2, 8, 18, 32, 18, 6 全元素の各電子殻の電子数を比較 →
識別子
- CAS登録番号
- 7440-08-6 全元素のCAS登録番号を比較 →
- 項記号
- 3P2
- InChI
- InChI=1S/Po
- InChI Key
- HZEBHPIOVYHPMT-UHFFFAOYSA-N
電子配置 測定値
Po: 4f¹⁴ 5d¹⁰ 6s² 6p⁴[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁴1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁴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 |
|---|---|---|---|
| 211 放射性 | 210.9866536 ± 0.0000014 | データなし | 516 ms |
| 193 放射性 | 192.991026 ± 0.000037 | データなし | 399 ms |
| 194 放射性 | 193.988186 ± 0.000014 | データなし | 392 ms |
| 212 放射性 | 211.9888684 ± 0.0000013 | データなし | 294.4 ns |
| 188 放射性 | 187.999416 ± 0.000021 | データなし | 270 us |
相／状態
理由: 融点（253.85 °C）より228.9 °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84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 |
|---|---|---|
| Po I | 0 | 33 |
| Po II | +1 | 2 |
| Po III | +2 | 2 |
| Po IV | +3 | 2 |
| Po V | +4 | 2 |
| Po VI | +5 | 2 |
| Po VII | +6 | 2 |
| Po VIII | +7 | 2 |
| Po IX | +8 | 2 |
| Po X | +9 | 2 |
イオン半径
| 電荷 | 配位 | スピン | 半径 |
|---|---|---|---|
| +4 | 6 | データなし | 94 pm |
| +4 | 8 | データなし | 108 pm |
| +6 | 6 | データなし | 67 pm |
化合物
同位体 (5)
Twenty five isotopes of polonium are known, with atomic masses ranging from 194 to 218. Polonium-210 is the most readily available. Isotopes of mass 209 (half-life 103 years) and mass 208 (half-life 2.9 years) can be prepared by alpha, proton, or deuteron bombardment of lead or bismuth in a cyclotron, but these are expensive to produce.
| 質量数 | 原子質量（u） | 天然存在比 | 半減期 | 崩壊形式 | |
|---|---|---|---|---|---|
| 211 放射性 | 210.9866536 ± 0.0000014 | データなし | 516 ms | α =100% | |
| 193 放射性 | 192.991026 ± 0.000037 | データなし | 399 ms | α ≈100%β+ ? | |
| 194 放射性 | 193.988186 ± 0.000014 | データなし | 392 ms | α ≈100%β+ ? | |
| 212 放射性 | 211.9888684 ± 0.0000013 | データなし | 294.4 ns | α =100% | |
| 188 放射性 | 187.999416 ± 0.000021 | データなし | 270 us | α ≈100%β+ ? |
詳細な性質
共有結合半径（詳細）
- 共有結合半径（Pyykkö）
- 145 pm
- 共有結合半径（Pyykkö、二重結合）
- 135 pm
- 共有結合半径（Pyykkö、三重結合）
- 129 pm
ファンデルワールス半径
- Truhlar
- 197 pm
- UFF
- 470.9 pm
- MM3
- 259 pm
原子半径と金属半径
- 原子半径（Rahm）
- 250 pm
番号付けの尺度
- Mendeleev
- 103
- Pettifor
- 91
- Glawe
- 93
電気陰性度の尺度
- Ghosh
- 0
- Gunnarsson–Lundqvist
- 6
- Robles–Bartolotti
- 4
分極率と分散
- 双極子分極率
- 44 a.u.
- 双極子分極率（不確かさ）
- 4 a.u.
- C₆ (Gould–Bučko)
- 424 Ha·Bohr6
相転移と同素体
| 融点 | 527.15 K |
| 沸点 | 1235.15 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 | 1.6232 |
| 2 | p | 4.5428 |
| 2 | s | 22.0782 |
| 3 | d | 13.428 |
| 3 | p | 23.2851 |
| 3 | s | 24.3813 |
| 4 | d | 36.3328 |
| 4 | f | 37.8416 |
| 4 | p | 36.3328 |
| 4 | s | 35.4784 |
結晶半径の詳細 (3)
| 電荷 | CN | スピン | rcrystal (pm) | 由来 |
|---|---|---|---|---|
| 4 | VI | 108 | from r^3 vs V plots, | |
| 4 | VIII | 122 | from r^3 vs V plots, | |
| 6 | VI | 81 | Ahrens (1952) ionic radius, |
同位体の崩壊形式 (71)
| 同位体 | モード | 強度 |
|---|---|---|
| 186 | A | 100% |
| 186 | p | — |
| 187 | A | 100% |
| 187 | B+ | — |
| 188 | A | 100% |
| 188 | B+ | — |
| 189 | A | 100% |
| 189 | B+ | — |
| 190 | A | 100% |
| 190 | B+ | — |
X線散乱因子 (516)
| エネルギー (eV) | f₁ | f₂ |
|---|---|---|
| 10 | — | 4.92763 |
| 10.1617 | — | 4.95784 |
| 10.3261 | — | 4.98823 |
| 10.4931 | — | 5.01881 |
| 10.6628 | — | 5.04957 |
| 10.8353 | — | 5.10634 |
| 11.0106 | — | 5.17368 |
| 11.1886 | — | 5.24191 |
| 11.3696 | — | 5.31104 |
| 11.5535 | — | 5.38108 |
追加データ
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
2×10-10 milligrams per kilogram
参考文献 (1)
- [5] Polonium https://education.jlab.org/itselemental/ele084.html
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
1.5×10-14 milligrams per liter
参考文献 (1)
- [5] Polonium https://education.jlab.org/itselemental/ele084.html
Sources
Sources of this element.
Polonium is a very rare natural element. Uranium ores contain only about 100 micrograms of the element per ton. Its abundance is only about 0.2% of that of radium.
In 1934, scientists discovered that when they bombarded natural bismuth (209Bi) with neutrons, 210Bi, the parent of polonium, was obtained. Milligram amounts of polonium may now be prepared this way, by using the high neutron fluxes of nuclear reactors.
参考文献 (1)
- [6] Polonium https://periodic.lanl.gov/84.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 Polonium.
The element property data was retrieved from publications.