Radon (Rn)
noble-gasGas
標準原子量
[222]電子配置
[Xe] 6s2 4f14 5d10 6p6融点
-71.15 °C沸点
-61.7 °C密度
9.73 kg/m³酸化数
0, +2, +6電気陰性度（Pauling）
データなし第1イオン化エネルギー
10.7485 eV発見年
1900原子半径
データなし詳細
Radon is a radioactive noble gas and the heaviest naturally occurring member of group 18. It is chemically inert compared with most elements, but its radioactivity makes it environmentally and medically important. Natural radon is produced mainly in uranium and thorium decay chains, especially as ²²²Rn from radium-226. Its gaseous form lets it migrate from rocks, soils, and building materials into air and enclosed spaces.
Radon is present in the atomosphere at very low concentrations. See Wikipedia for discussion of concentration. At ordinary temperatures radon is a colorless gas; when cooled below the freezing point, radon exhibits a brilliant phosphorescence which becomes yellow as the temperature is lowered and orange-red at the temperature of liquid air. It has been reported that fluorine reacts with radon, forming a fluoride. Radon clathrates have also been reported.
Radon was discovered by Friedrich Ernst Dorn, a German chemist, in 1900 while studying radium's decay chain. Originally named niton after the Latin word for shining, nitens, radon has been known as radon since 1923. Today, radon is still primarily obtained through the decay of radium. At normal room temperatures, radon is a colorless, odorless, radioactive gas. The most common forms of radon decay through alpha decay. Alpha decay usually isn't considered to be a great radiological hazard since the alpha particles produced by the decay are easily stopped. However, since radon is a gas, it is easily inhaled and living tissue is directly exposed to the radiation. Although it has a relatively short half-life, radon decays into longer lived, solid, radioactive elements which can collect on dust particles and be inhaled as well. For these reasons, there is some concern as to the amount of radon present within homes. Radon seeps into houses as a result of the decay of radium, thorium or uranium ores underground and varies greatly from location to location. On average, the earth's atmosphere is 0.0000000000000000001% radon.
When cooled to its solid state, radon glows yellow. The glow becomes orange-red as the temperature is lowered.
Radon's most stable isotope, radon-222, has a half-life of about 3.8 days. It decays into polonium-218 through alpha decay.
The name was derived from radium; called niton at first, from the Latin word nitens meaning shining.The element was discovered in 1900 by Dorn, who called it radium emanation. In 1908 Ramsay and Gray, who named it niton, isolated the element and determined its density, finding it to be the heaviest known gas. It is essentially inert and occupies the last place in the zero group of gases in the Periodic Table. Since 1923, it has been called radon.
Pure radon is a colorless, odorless, monatomic gas at ordinary temperature and pressure. It can be condensed at low temperature to a liquid and then a solid, but macroscopic handling is limited by intense radioactivity and radiolytic effects.
Radon has no broad commercial use. Historically, sealed radon sources were used in some radiotherapy practices before safer and more controllable radionuclides became preferred. It has also been used as a tracer in hydrology, geology, and atmospheric studies because it is continuously generated in rocks and has isotope-dependent decay times. Present use is mainly analytical or research-related, including calibration and environmental measurement work.
Small amounts of radon are sometimes used by hospitals to treat some forms of cancer. Radon fluoride (RnF) is the only confirmed compound of radon.
Radon is still produced for therapeutic use by a few hospitals by pumping it from a radium source and sealing it in minute tubes, called seeds or needles, for application to patient. This practice has been largely discontinued as hospitals can get the seeds directly from suppliers, who make up the seeds with the desired activity for the day of use.
Isotopes in Earth/Planetary Science
Both 220Rn and 222Rn (with half-lives of 56 s and 3.8 days, respectively) are used to study underground environmental and atmospheric gaseous-transport processes [568] United States Geological Survey. Resources on Isotopes-Periodic Table-Radon, U.S. Geological Survey (2014), Feb. 25; http://wwwrcamnl.wr.usgs.gov/isoig/period/rn_iig.html., [569] State of California Department of Conservation. Indoor Radon, State of California Department of Conservation (2017), April 8; http://www.consrv.ca.gov/CGS/minerals/hazardous_minerals/radon/Pages/index.aspx., [570] L. S. Quindos Poncela, C. Sainz Fernandez, I. Fuente Merino, J. L. Gutierrez Villanueva, A. Gonzalez Diez. Acta Geophysica.61, 848 (2013).. The interaction of radon with streams and rivers enables it to be used as a tracer in groundwater studies (Fig. IUPAC.86.1). 222Rn has a short residence time in streams and river channels, which leads to radon loss. As a result, if an area of a stream or river has a high concentration of radon, it suggests that there are local groundwater inputs [568] United States Geological Survey. Resources on Isotopes-Periodic Table-Radon, U.S. Geological Survey (2014), Feb. 25; http://wwwrcamnl.wr.usgs.gov/isoig/period/rn_iig.html., [569] State of California Department of Conservation. Indoor Radon, State of California Department of Conservation (2017), April 8; http://www.consrv.ca.gov/CGS/minerals/hazardous_minerals/radon/Pages/index.aspx., [570] L. S. Quindos Poncela, C. Sainz Fernandez, I. Fuente Merino, J. L. Gutierrez Villanueva, A. Gonzalez Diez. Acta Geophysica.61, 848 (2013).. In a deep (100 m) contaminated aquifer at a refinery site in Mexico, where the contaminated source was too deep to be directly accessible for sampling, Schubert et al. [571] M. Schubert, M. Balcazar, A. Lopez, P. Peña, J. H. Flores, K. Knöller. Isot. Environ. Health Stud.43, 215 (2007). collected groundwater samples from a few wells available at the site. They used the partitioning of the natural tracer 222Rn between uncontaminated groundwater and the NAPL (non-aqueous phase-liquid, such as oil, gasoline, and petroleum) source zone, and they were able to approximately identify the location of the NAPL source zone. As noted in Section 4.88.1, 222Rn has been used to quantify submarine groundwater discharge [572] R. N. Peterson, W. C. Burnett, M. Taniguchi, J. Chen, I. R. Santos, T. Ishitobi. J. Geophys. Res.113, C09021 (2008)..
Isotopes in Geochronology
222Rn has been used as a tool to date groundwater in combination with other isotopes or elemental ratios (i.e. helium/radon and xenon/radon amount ratios) [568] United States Geological Survey. Resources on Isotopes-Periodic Table-Radon, U.S. Geological Survey (2014), Feb. 25; http://wwwrcamnl.wr.usgs.gov/isoig/period/rn_iig.html., [574] T. F. Kraemer, D. P. Genereux. “Applications of uranium- and thorium-series radionuclides in catchment hydrology studies”, in Isotope Tracers in Catchment Hydrology, C. Kendall, J. J. McDonnell (Eds.), Elsevier, Amsterdam (1998)..
Radon is the least chemically studied noble gas because its isotopes are radioactive and available only in small amounts. The most established chemistry involves strong oxidizing and fluorinating conditions, with radon difluoride (RnF₂) reported as a radon compound. Ionic or complex fluoride species have been inferred in matrix and tracer experiments, but many details remain uncertain. Oxidation states above 0 are possible in principle, yet radon chemistry is much less developed than xenon chemistry.
See more information at the Radon compound page.
Radon is hazardous chiefly because inhaled radioactive decay products can lodge in the respiratory tract and irradiate tissue with alpha particles. The risk depends strongly on isotope, concentration, ventilation, exposure time, and the behavior of short-lived progeny such as polonium isotopes. Radon is also an asphyxiant like other gases if present at very high concentrations, but radiation exposure is the practical concern.
Care must be taken in handling radon, as with other radioactive materials. The main hazard is from inhalation of the element and its solid daughters which are collected on dust in the air. Good ventilation should be provided where radium, thorium, or actinium is stored to prevent build-up of the element. Radon build-up is a health consideration in uranium mines. Recently radon build-up in homes has been a concern. Many deaths from lung cancer are caused by radon exposure. In the U.S. it is recommended that remedial action be taken if the air in homes exceeds 4 pCi/l.
Radon forms naturally where uranium or thorium decay occurs in minerals and soils. Being a gas, it can diffuse through pore spaces, dissolve to some extent in groundwater, and enter buildings through cracks or service penetrations. Outdoors it is usually diluted rapidly, while enclosed or poorly ventilated spaces can accumulate higher concentrations. Its decay products attach to aerosols and surfaces, changing their mobility and exposure pathways.
Radon is not traded as a normal industrial commodity. It is generated continuously by decay of radium in sealed sources or collected in small quantities for specialized calibration and research needs. Supply is constrained less by elemental scarcity than by radiological controls, isotope half-lives, and the limited demand for handling the gas. Most practical applications that once used radon have been replaced by other radionuclides, electronic instruments, or direct environmental monitoring methods.
Formed from the decay of radium in the earths crust.
Radon has no stable isotopes, so it cannot accumulate over geological or cosmic timescales. In nature it appears only as a transient daughter in decay chains of long-lived heavy nuclides such as uranium and thorium. In extraterrestrial materials, any radon would likewise be short-lived and locally produced rather than primordial.
- Radon is the densest noble gas encountered naturally on Earth.
- The isotope ²²²Rn has a half-life of about 3.8 days, long enough for migration through soil.
- Radon was once called niton, a name reflected in the old symbol Nt.
- Indoor radon levels often vary with season, pressure differences, and building ventilation.
- Radon measurements can reveal subsurface gas movement and some groundwater interactions.
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
- 220 pm 全元素のファンデルワールス半径を比較 →
- 密度
- 9.73 kg/m³ 全元素の密度を比較 →
- 標準温度・圧力（STP）での相
- 気体 全元素の標準温度・圧力（STP）での相を比較 →
- 融点
- -71.15 °C 全元素の融点を比較 →
- 沸点
- -61.7 °C 全元素の沸点を比較 →
- 熱伝導率
- 0.004 W/(m·K) 全元素の熱伝導率を比較 →
- 比熱容量
- 0.094 J/(g·K) 全元素の比熱容量を比較 →
- モル熱容量
- 20.786 J/(mol·K) 全元素のモル熱容量を比較 →
- 結晶構造
- 面心立方構造 全元素の結晶構造を比較 →
化学的性質
- 電気陰性度（Allen）
- 2.6
- 電子親和力
- -0.7 eV (負の値—この原子は電子を取り込まないと予測される)
- 第1イオン化エネルギー
- 10.7485 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
- 18.990065 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
- 29.400101 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
- 36.900127 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
- 52.900182 eV 全元素の第5イオン化エネルギーを比較 →
- 酸化数
- 0, +2, +6 全元素の酸化数を比較 →
- 価電子
- 8 全元素の価電子を比較 →
- 電子配置
- [Xe] 6s2 4f14 5d10 6p6
熱力学的性質
- 三重点（温度）
- -71 °C
- 三重点（圧力）
- 5.1e+4 Pa
- 臨界点（温度）
- 104 °C
- 臨界点（圧力）
- 6.28e+6 Pa
- 融解熱
- 0.03109292 eV 全元素の融解熱を比較 →
- 蒸発熱
- 0.16582889 eV 全元素の蒸発熱を比較 →
- 原子化熱
- 0 eV
原子核
- 陽子数
- 86 全元素の陽子数を比較 →
- 中性子数
- 136 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）
- 222
- 最も安定な同位体
- Rn-222
- 発見年
- 1900
存在度
- 存在度（地殻）
- 4e-13 mg/kg 全元素の存在度（地殻）を比較 →
- 存在度（海洋）
- 6 × 10−16 mg/L 全元素の存在度（海洋）を比較 →
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, 8 全元素の各電子殻の電子数を比較 →
識別子
- CAS登録番号
- 10043-92-2 全元素のCAS登録番号を比較 →
- 項記号
- 1S0
- InChI
- InChI=1S/Rn
- InChI Key
- SYUHGPGVQRZVTB-UHFFFAOYSA-N
電子配置 測定値
Rn: 4f¹⁴ 5d¹⁰ 6s² 6p⁶[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁶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 |
|---|---|---|---|
| 194 放射性 | 194.006144 ± 0.000018 | データなし | 780 us |
| 217 放射性 | 217.003928 ± 0.0000045 | データなし | 593 us |
| 199 放射性 | 198.99839 ± 0.000068 | データなし | 590 ms |
| 214 放射性 | 213.995363 ± 0.0000099 | データなし | 259 ns |
| 205 放射性 | 204.991719 ± 0.000054 | データなし | 170 秒 |
相／状態
理由: 沸点（-61.7 °C）より86.7 °C高い
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
密度
標準条件下
現在の温度Tにおいて理想気体の状態方程式で推定
詳細
原子スペクトル
全86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 |
|---|---|---|
| Rn I | 0 | 127 |
| Rn II | +1 | 3 |
| Rn III | +2 | 2 |
| Rn IV | +3 | 2 |
| Rn V | +4 | 2 |
| Rn VI | +5 | 2 |
| Rn VII | +6 | 2 |
| Rn VIII | +7 | 2 |
| Rn IX | +8 | 2 |
| Rn X | +9 | 2 |
固相の結晶構造データはありません
結晶構造: fcc
化合物
同位体 (5)
Thirty-nine isotopes are known. Radon-222 is the most common. It has a half-life of 3.823 days and is an alpha emitter. It is estimated that every square mile of soil to a depth of 6 inches contains about 1 g of radium, which releases radon in tiny amounts into the atmosphere. Radon gas can collect in buildings, creating a health risk. The Environmental Protection Agency estimates that responsible for an estimated 20,000 lung cancer deaths each year. More on radon and health. Radon is present in some spring waters, such as those at Hot Springs, Arkansas.
| 質量数 | 原子質量（u） | 天然存在比 | 半減期 | 崩壊形式 | |
|---|---|---|---|---|---|
| 194 放射性 | 194.006144 ± 0.000018 | データなし | 780 us | α ≈100%β+ ? | |
| 217 放射性 | 217.003928 ± 0.0000045 | データなし | 593 us | α =100% | |
| 199 放射性 | 198.99839 ± 0.000068 | データなし | 590 ms | α ≈100%β+ ? | |
| 214 放射性 | 213.995363 ± 0.0000099 | データなし | 259 ns | α =100% | |
| 205 放射性 | 204.991719 ± 0.000054 | データなし | 170 秒 | β+ =75.4±0.9%α =24.6±0.9% |
詳細な性質
共有結合半径（詳細）
- 共有結合半径（Pyykkö）
- 142 pm
- 共有結合半径（Pyykkö、二重結合）
- 145 pm
- 共有結合半径（Pyykkö、三重結合）
- 133 pm
ファンデルワールス半径
- Truhlar
- 220 pm
- Alvarez
- 240 pm
- UFF
- 476.5 pm
- MM3
- 243 pm
原子半径と金属半径
- 原子半径（Rahm）
- 243 pm
番号付けの尺度
- Mendeleev
- 117
- Pettifor
- 6
- Glawe
- 6
電気陰性度の尺度
- Ghosh
- 0
- Gunnarsson–Lundqvist
- 4
- Robles–Bartolotti
- 4
分極率と分散
- 双極子分極率
- 35 a.u.
- 双極子分極率（不確かさ）
- 2 a.u.
- C₆ (Gould–Bučko)
- 408 Ha·Bohr6
希ガスの性質
| HALOGENS | RnF2 |
相転移と同素体
| 融点 | 202.15 K |
| 沸点 | 211.45 K |
| 臨界点（温度） | 377.15 K |
| 臨界点（圧力） | 6.28 MPa |
酸化数の分類
専門参考データ
遮蔽定数 (15)
| n | 軌道 | σ |
|---|---|---|
| 1 | s | 1.6659 |
| 2 | p | 4.562 |
| 2 | s | 22.5864 |
| 3 | d | 13.4027 |
| 3 | p | 23.7194 |
| 3 | s | 24.9149 |
| 4 | d | 38.0572 |
| 4 | f | 37.6688 |
| 4 | p | 36.6988 |
| 4 | s | 35.85 |
同位体の崩壊形式 (59)
| 同位体 | モード | 強度 |
|---|---|---|
| 193 | A | 100% |
| 194 | A | 100% |
| 194 | B+ | — |
| 195 | A | 100% |
| 196 | A | 100% |
| 196 | B+ | — |
| 197 | A | 100% |
| 197 | B+ | — |
| 198 | A | 93% |
| 198 | B+ | — |
X線散乱因子 (516)
| エネルギー (eV) | f₁ | f₂ |
|---|---|---|
| 10 | — | 2.83964 |
| 10.1617 | — | 3.21791 |
| 10.3261 | — | 3.64656 |
| 10.4931 | — | 4.05083 |
| 10.6628 | — | 4.4288 |
| 10.8353 | — | 4.83437 |
| 11.0106 | — | 5.24445 |
| 11.1886 | — | 5.68932 |
| 11.3696 | — | 6.15277 |
| 11.5535 | — | 6.62072 |
追加データ
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
4×10-13 milligrams per kilogram
参考文献 (1)
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
6×10-16 milligrams per liter
参考文献 (1)
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 Radon.
The element property data was retrieved from publications.