rubidium

Japanese: ルビジウム

Rb. Atomic number 37. Periodic table group 1 alkali metal element with electron configuration 1s2 ^2s2 ^2p6 ^3s2 ^3p6 ^3d10 ^4s2 ^4p6 ^5s1 ^. Atomic weight 85.47. There is one stable isotope and 14 radioactive isotopes. In nature, non-radioactive ⁸⁵ Rb (72.165%) and radioactive ⁸⁷ Rb (27.835%) exist. It was discovered by RWE Bunsen and GR Kirchhoff in 1861 through spectroscopic analysis.
Rubidium is naturally found in small amounts in ores such as lepidolite and mineral springs. Its abundance in the earth's crust is 32 ppm. The metal is obtained by heating rubidium chloride with calcium in a vacuum and reducing it. It is a soft, silvery-white metal. It has a body-centered cubic lattice structure. The lattice constant a = 0.562 nm. The metallic bond radius is 2.47 Å. Its density is 1.53 g cm ^-3 (20 °C). Its melting point is 38.89 °C, and its boiling point is 688 °C. Its first ionization energy is 4.176 eV. Its flame color reaction is reddish purple, and its name comes from the Latin rubidus, which indicates its color. Its chemical properties are similar to those of calcium, but it is more active. It oxidizes immediately in air, causing the surface to become cloudy, but at high temperatures it produces the superoxide RbO _2. It directly combines with hydrogen and halogens. It reacts violently with water to produce hydrogen and hydroxide. It forms an amalgam with mercury and a solid solution with other alkali metals. In compounds it always exists as a cation with oxidation number 1. Its salts are isomorphous to the potassium salt and have similar solubility in water.
It is used in vacuum tube getters and photovoltaic cells. ⁸⁷ Rb decays to ⁸⁷ Sr, which has a long half-life of 4.8 x 10 ¹⁰ y, so it is used to date rocks older than 10 ⁷ y (rubidium-strontium dating method). Rubidium salts are used as raw materials in the manufacture of glass and ceramics. [CAS 7440-17-7]

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

Japanese:

Rb．原子番号37の元素．電子配置1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶5s¹の周期表1族アルカリ金属元素．原子量85.47．1種類の安定同位体と14種類の放射性同位体がある．天然には，非放射性の⁸⁵Rb(72.165％)と放射性の⁸⁷Rb(27.835％)が存在する．1861年R.W.E. Bunsen(ブンゼン)とG.R. Kirchhoffが分光分析により発見した．
天然には，紅雲母(リチア雲母，鱗雲母)などの鉱石や鉱泉中に少量見いだされる．地殻中の存在度32 ppm．金属は塩化ルビジウムを真空中でカルシウムと熱し，還元すると得られる．銀白色の軟らかい金属．体心立方格子構造．格子定数a ＝ 0.562 nm．金属結合半径2.47 Å．密度1.53 g cm^－3(20 ℃)．融点38.89 ℃，沸点688 ℃．第一イオン化エネルギー4.176 eV．炎色反応は紅紫色で，元素名は，その色を示すラテン語rubidusに由来する．化学的性質はカルシウムに似ているが，より活性が高い．空気中でただちに酸化されて表面がくもるが，高温では超酸化物RbO₂を生じる．水素，ハロゲンと直接化合する．水とはげしく反応して水素と水酸化物を生じる．水銀とアマルガムをつくり，ほかのアルカリ金属とは固溶体をつくる．化合物中ではつねに酸化数1の陽イオンとして存在する．塩はカリウム塩と同形で，水に対する溶解性も類似している．
真空管のゲッターや光電池に用いられる．また，⁸⁷Rbはβ崩壊して⁸⁷Srになるが，その半減期が4.8×10¹⁰ y と長いので，10⁷ y よりも古い岩石の年代測定に利用される(ルビジウム-ストロンチウム年代測定法)．ルビジウム塩はガラスや陶磁器の製造原料に用いられる．[CAS 7440-17-7]