krypton

Kr. Atomic number 36. Electron configuration [Ar]3d ¹⁰ 4s ² 4p ^6. Atomic mass 83.798(2). There are six stable isotopes with mass numbers 78 (0.355(3)%), 80 (2.286(10)%), 82 (11.593(31)%), 83 (11.500(19)%), 84 (56.987(15)%), and 86 (17.279(41)%). There are 27 known radionuclides with mass numbers between 69 and 97. ⁸¹ Kr is the longest-lived, decaying to ⁸¹ Br by orbital electron capture with a half-life of 2.29 × 10 ⁵ y. The most important nuclide is krypton ⁸⁵ (Kr), a fission product, a beta-decay nuclide with a half-life of 10.78 y. It was discovered in 1898 by W. Ramsay and MW Travers during the fractional distillation of liquid air. Its name comes from the Greek κρνπτοζ, meaning "hidden one". It is present in the atmosphere at 1.14 ppm by volume, and in the atmosphere of Mars at 0.3 ppm by volume. It is obtained from the last fraction of liquid air fractional distillation. It is a colorless, odorless gas. Its melting point is −157.36 °C, its boiling point is −152.3 °C, its critical temperature is −63.69 °C (209.46 K), and its triple point is −157.39 °C (115.76 K). Its density is 2.443 g cm ⁻³ (115.77 K, liquid). First ionization energy 1350.7 kJ mol ^-1 (13.9996 eV). Although it is chemically inert, KrF ₂ was synthesized in 1963 (see Alternative Terms) Kr compound. Its orange-red emission spectrum is used in airport lighting and projection lamps. Krypton gas lasers are used in retinal surgery. Until the International Conference of Weights and Measures in 1983 made the speed of light in a vacuum the standard, 1 m was defined as 1650763.73 times the wavelength of the orange-red spectrum of ⁸⁶ Kr (605.780211 nm). [CAS 7439-90-9]

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

Kr．原子番号36の元素．電子配置[Ar]3d¹⁰4s²4p⁶の周期表18族希ガス元素．原子量83.798(2)．安定同位体核種は，質量数78(0.355(3)％)，80(2.286(10)％)，82(11.593(31)％)，83(11.500(19)％)，84(56.987(15)％)，86(17.279(41)％)の6種．質量数69～97までの27種の放射性核種が知られている．⁸¹Kr がもっとも長寿命で，半減期2.29×10⁵ y で軌道電子捕獲により ⁸¹Br に崩壊する．もっとも重要な核種は，核分裂生成物の一つである ⁸⁵Kr(クリプトン85)で，半減期10.78 y のβ崩壊核種．1898年，W. Ramsay(ラムゼー)とM.W. Traversによって液体空気の分留中に発見された．ギリシア語の“かくされたもの”(κρνπτοζ)から名づけられた．大気中に1.14体積 ppm，火星の大気中にも0.3体積 ppm 存在する．液体空気の分留最後の留分から得られる．無色，無臭の気体．融点－157.36 ℃，沸点－152.3 ℃，臨界温度－63.69 ℃(209.46 K)，三重点－157.39 ℃(115.76 K)．密度2.443 g cm^－3(115.77 K，液体)．第一イオン化エネルギー1350.7 kJ mol^－1(13.9996 eV)．化学的に不活性であるが，1963年にKrF₂が合成された([別用語参照]クリプトン化合物)．用途は，橙赤色の発光スペクトル線を利用して，空港等の施設の照明灯，投影用ランプ充填ガスなど．クリプトンガスレーザーは網膜などの手術に使われる．1983年の国際度量衡機構総会で真空中の光速を基準にするまで，1960年から ⁸⁶Kr の橙赤色スペクトル線の波長605.780211 nm の1650763.73倍が1 m と定義されていた．[CAS 7439-90-9]

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