xenon

Japanese: キセノン

Xe. Atomic number 54. Electron configuration [Kr]4d ¹⁰ 5s ² 5p ^6. Noble gas element in group 18 of the periodic table. Atomic weight 131.293(6). Naturally occurring isotopes are very abundant, with mass numbers 124 (0.0952%), 126 (0.0890), 128 (1.910), 129 (26.4006), 130 (4.0710), 131 (21.2324), 132 (26.9086), 134 (10.4357), and 136 (8.8573). It occupies 0.087 ppm by volume of dry air. There are more than 40 radioactive nuclides with mass numbers between 109 and 147, with 127 having a half-life of 36.4 d, ¹³⁶ Xe having a half-life of > 2.4× ¹⁰²¹ y, ^{and 124} Xe having a half-life of 1.1× ¹⁰¹⁷ y, and existing in the atmosphere. ¹³⁵ Xe, produced during uranium fission, has a large thermal neutron absorption cross section (2.6× ¹⁰⁶ barns) and is known as a neutron poison because it interferes with the operation of nuclear reactors. It was discovered in 1898 by W. Ramsay and MW Travers in the Kr fraction during the fractional distillation of liquid air. It was named after the Greek word ξενοσ, meaning "stranger."
It exists at 0.087 ppm by volume in the atmosphere, and 0.08 ppm by volume in the Martian atmosphere. It is obtained from the last fraction of liquid air distillation and is purified by fractional adsorption with activated charcoal, evaporation, and gas chromatography. It is a colorless, odorless gas. Metallic xenon has been produced at hundreds of thousands of atm. Its melting point is 161.3 K (-111.9 °C), its boiling point is 165 K (-108.1 °C). Its critical temperature is 256.5 K (16.6 °C). Its triple point is 161.3 K. It is heavy, with a liquid density of 2.939 g cm ^-3 (boiling point) and a solid density of 3.54 g cm ^-3 (triple point). Its first ionization energy is 1170.4 kJ mol ^-1 (12.13 eV). Prior to 1962, it was mistakenly thought to be completely inert, but in the same year, N. Bartlett of Canada synthesized _XePtF6 , and subsequently fluorides, oxides, and fluoride oxides were synthesized. Oxidation numbers 2, 4, 6, and 8. It reacts easily with fluorine, and colorless crystals of _XeF2 can be obtained by simply placing a mixture of Xe and _F2 in a glass container and exposing it to sunlight. Xe itself is non-toxic, but the compounds it produces are toxic due to their strong oxidizing power.
Its applications include xenon lamps that use discharges in Xe; because its emission spectrum is similar to sunlight, it is used as a white light source in photographic flash lamps, lighthouse lamps, and more recently, due to its high brightness, in automobile headlights. Liquids are used as a medium in particle physics detectors (neutrinos, dark matter) and imaging devices. [CAS 7440-63-3]

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

Japanese:

Xe．原子番号54の元素．電子配置[Kr]4d¹⁰5s²5p⁶の周期表18族希ガス元素．原子量131.293(6)．天然に存在する同位体核種は質量数124(0.0952％)，126(0.0890)，128(1.910)，129(26.4006)，130(4.0710)，131(21.2324)，132(26.9086)，134(10.4357)，136(8.8573)と非常に多い．乾燥大気の0.087体積 ppm を占める．放射性核種は質量数109～147の間に40種以上あり，127のものが半減期36.4 d，¹³⁶Xe は＞ 2.4×10²¹ y．¹²⁴Xe は1.1×10¹⁷ y で大気中に存在する．ウラン核分裂の際に生成される ¹³⁵Xe は熱中性子吸収断面積が大きく(2.6×10⁶ バーン)，原子炉運転の際に障害となるので中性子毒として知られる．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Kr留分から発見された．ギリシア語の“よそ者”ξενοσから名づけられた．
大気中に0.087体積 ppm，火星の大気中にも0.08体積 ppm 存在する．液体空気の分留最後の留分から得られ，活性炭による分別吸着，蒸発，ガスクロマトグラフィーによって精製される．無色，無臭の気体．数十万atm 下で金属キセノンがつくられた．融点161.3 K(－111.9 ℃)，沸点165 K(－108.1 ℃)．臨界温度256.5 K(16.6 ℃)．三重点161.3 K．液体の密度2.939 g cm^－3(沸点)，固体の密度3.54 g cm^－3(三重点)と重い．第一イオン化エネルギー1170.4 kJ mol^－1(12.13 eV)．1962年以前は誤ってまったく不活性と思われていたが，同年，カナダのN. BartlettによりXePtF₆が合成され，その後，フッ化物や酸化物，フッ化酸化物が合成された．酸化数2，4，6，8．フッ素との反応は容易に起こり，XeF₂はXeと F₂ の混合気体をガラス容器に入れ，太陽光を当てるだけで無色の結晶が得られる．Xe自体は無毒であるが，化合物は酸化力が強いために有毒である．
用途は，Xe中の放電を利用したキセノンランプ用で，発光スペクトルが太陽光に似ているので白色光源として写真用のフラッシュランプ，灯台用ランプ，最近では高輝度を利用して自動車のヘッドライト用にも用いられる．液体は素粒子物理学用の検出器(ニュートリノ，暗黒物質)やイメージングデバイスに媒質として使用される．[CAS 7440-63-3]