rhenium

Re. Element with atomic number 75. Electron configuration [Xe] ^{4f145d56s2 .} DI Mendeleev's dvi-manganese ⁽ dvi, from Sanskrit 2 → eka element). Atomic weight 186.207(1). Naturally occurring isotope ¹⁸⁵ Re (37.40(2)%) and β ^- decay (half-life 4.12 × ^1011y ) nuclide ¹⁸⁷ Re (62.60(2)%). Radioisotope nuclides with mass numbers from 160 to 194 are known. Discovered in 1925 by WKF Noddack, I. Tacke-Noddack, and O. Berg, it was named after the Latin name of the Rhine river, Rhenus. In 1908, Masataka Ogawa (later the president of Tohoku Imperial University) isolated an element from thoriumite under the guidance of W. Ramsay and mistakenly named it nipponium, an element with atomic number 43. It was later discovered that this was in fact rhenium, one period lower.
Abundance in the earth's crust: 0.0005 ppm. Rhenium resources are unevenly distributed, with 50% of the reserves found in Chile, followed by the United States and Kazakhstan. Rhenium has no endogenous mineral, but is concentrated mainly in copper and sulfide minerals formed at high temperatures, such as molybdenite (0.6-21 g per ton of molybdenite). Re ₂ O ₇ in the dust from the roasting of molybdenite is treated to obtain ammonium tetraoxorhenate(VII), NH ₄ ReO ₂ , which is then reduced with hydrogen to obtain the metal. Silvery-white metal with a hexagonal close-packed structure. Powder is black or dark gray. Melting point: 3180 °C, boiling point: 5596 °C. Density: 21.02 g cm ^-3 . First ionization energy: 7.76 eV. Superconducting below 1.70 K. Oxidation state: wide range: -1 to 7. Its chemical properties are similar to those of manganese in some ways, but its main oxidation numbers are 4 to 7, which is different from Mn's 2. It is stable in air at room temperature, but is oxidized to volatile Re ₂ O ₇ at temperatures above 300 °C. It is insoluble in hydrofluoric acid and hydrochloric acid, but soluble in concentrated sulfuric acid, concentrated nitric acid, and hydrogen peroxide. It reacts with fluorine to form ReF ₆ , and with chlorine and bromine at high temperatures to form ReX ₅ compounds. It forms amalgam with mercury.
Its main uses are as a component of nickel-based superalloys for aircraft jet engines and gas turbines, and platinum-rhenium catalysts for petroleum reforming. Rhenium alloys are also used as crucible materials, electrical contacts, and filaments for electron tubes, mass spectrometers, vacuum gauges, etc. due to their high thermionic emission. [CAS 7440-15-5]

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

Re．原子番号75の元素．電子配置[Xe]4f ¹⁴5d⁵6s²の周期表7族遷移金属元素．D.I. Mendeleev(メンデレーエフ)のdvi-マンガン(dvi，サンスクリット語の2→エカ元素)．原子量186.207(1)．天然に安定同位体 ¹⁸⁵Re(37.40(2)％)と β^－ 崩壊(半減期4.12×10¹¹ y)核種 ¹⁸⁷Re(62.60(2)％)が存在する．質量数160から194までの放射性同位体核種が知られている．1925年，W.K.F. Noddack(ノダック)とI. Tacke-Noddack，O. Bergにより発見され，ライン川のラテン名Rhenusから命名された．1908年に，小川正孝(後に東北帝国大学総長)がW. Ramsay(ラムゼー)のもとで方トリウム石から分離し，原子番号43の元素と誤ってnipponiumと名づけたものは，じつは一周期下のレニウムであったことが後年判明した．
地殻中の存在度0.0005 ppm．レニウム資源は偏在しており，埋蔵量の50％ がチリ，ついでアメリカ，カザフスタンである．レニウムには固有の鉱物はなく，主として高温で生成した銅，硫化鉱物，たとえば輝水鉛鉱中に濃縮している(1 t の輝水鉛鉱中に0.6～21 g)．輝水鉛鉱ばい焼の煙灰中のRe₂O₇を処理してテトラオキソレニウム(Ⅶ)酸アンモニウムNH₄ReO₂として得，これを水素で還元して金属を得る．銀白色の六方最密構造の金属．粉末は黒色または暗灰色．融点3180 ℃，沸点5596 ℃．密度21.02 g cm^－3．第一イオン化エネルギー7.76 eV．1.70 K 以下で超伝導．酸化数－1～7で範囲が広い．化学的な性質はマンガンに似ている点もあるが，主要な酸化数は4～7で，Mnの2とは異なる．室温の空気中で安定であるが，300 ℃ 以上で酸化されて揮発性のRe₂O₇となる．フッ化水素酸，塩酸には不溶，濃硫酸，濃硝酸，過酸化水素に可溶．フッ素と反応してReF₆，塩素，臭素とは高温で反応してReX₅化合物となる．水銀とアマルガムをつくる．
おもな用途は，航空機用ジェットエンジン，ガスタービン用ニッケル-ベース超合金と，石油改質用白金-レニウム触媒の成分である．レニウム合金は，そのほか，るつぼ材，電気接点，熱電子放出能力が高いことから電子管材料，質量分析計，真空計などのフィラメントに使用される．[CAS 7440-15-5]

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