tungsten

W. Element with atomic number 74. Element in group ⁶ of the periodic table ^with the electron configuration [Xe] ^4f145d46s2 . Atomic weight 183.84(1). Natural isotope abundances are ¹⁸⁰ W 0.12(1)%, ¹⁸² W 26.50(16)%, ¹⁸³ W 14.31(4)%, ¹⁸⁴ W 30.64(2)%, ^{and 186} W 28.43(19)%. Thirty radioactive nuclides with mass numbers ranging from 158 to 190 have been produced. The name of the element comes from the Swedish word tung sten, which means "heavy stone". The element symbol is the initials of the German name Wolfram.
In 1771, KCW Scheele of Sweden discovered that an acid could be produced from elements in tungsten minerals, and in 1783, the de Elhuyar brothers of Spain succeeded in isolating the metal by reducing the acid with charcoal. Its abundance in the earth's crust is 1.0 ppm. The main minerals are sheelite (CaWO ₄ ) and wolframite ((Fe,Mn)WO ₄ ), and it is found in China, Russia, Canada, Austria, and other countries as a resource. China is the main producer, accounting for about 85% of the world's production. Its reserves are also about 65%. Mining in Japan ceased in 1992. It is one of the ores covered by the National Rare Metal Stockpiling System that began in 1983. The above minerals are treated with alkali roasting to obtain the oxide WO ₃ , which is then reduced with hydrogen or carbon to obtain the metal. Recycling of tungsten products is also an important resource. Domestic ore processing has also been halted, and most imports now rely on intermediate raw materials such as tungsten carbide from China. The pure metal is gray-white and soft. Density is 19.3 g cm ^-3 . Maximum melting point is 3410 °C, boiling point is 5700 °C. First ionization energy is 733.2 kJ mol ^-1 (7.60 eV). It reacts with oxygen at high temperatures to form WO ₃ trioxide. It reacts with fluorine at room temperature to form WF ₆ hexafluoride. It also reacts easily with chlorine to form WF 6 hexachloride. Oxidation number 1 to 6. It is not affected by ordinary acids or dilute alkaline solutions. It does not react with water at room temperature.
The metal is used in incandescent light bulbs, fluorescent light filaments, electron tubes, cathode ray tube electrodes, and X-ray tube targets. Alloys with steel and tungsten carbide are used as cemented carbides in high-speed cutting tools, the strong, corrosion-resistant alloy Hastelloy is an alloy with Ni, Cr, and Mo, calcium tungstate is a phosphor for fluorescent lamps, and tungsten sulfide is used as a high-temperature lubricant. [CAS 7440-33-7]

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

W．原子番号74の元素．電子配置[Xe]4f ¹⁴5d⁴6s²の周期表6族遷移金属元素．原子量183.84(1)．天然同位体存在比は ¹⁸⁰W 0.12(1)％，¹⁸²W 26.50(16)％，¹⁸³W 14.31(4)％，¹⁸⁴W 30.64(2)％，¹⁸⁶W 28.43(19)％．質量数158～190までの30種の放射性核種がつくられている．元素名はスウェーデン語の“重い石”を意味するtung stenから．元素記号はドイツ語の名称ウォルフラム(Wolfram)の頭文字．
1771年，スウェーデンのK.C.W. Scheele(シェーレ)がタングステン鉱物中の元素から酸ができることを見いだし，1783年，スペインのde Elhuyar兄弟がこの酸を木炭で還元して金属の単離に成功した．地殻中の存在度1.0 ppm．主要鉱物は灰重石(sheelite，CaWO₄)，鉄マンガン重石(wolframite，(Fe，Mn)WO₄)などで，資源として中国，ロシア，カナダ，オーストリアなどに産出する．中国が主要産出国で世界の産出量の約85％ を占める．埋蔵量も約65％．日本国内採鉱は1992年に停止．1983年からはじまったレアメタル国家備蓄制度の対象鉱種の一つ．上記の鉱物をアルカリばい焼で処理して酸化物WO₃を得て，水素または炭素で還元して金属を得る．タングステン製品のリサイクルも重要資源である．国内では鉱石処理も停止され，ほとんど中国からの炭化タングステンなどの中間原料輸入によっている．純粋な金属は灰白色で軟らかい．密度19.3 g cm^－3．融点3410 ℃ で最高，沸点5700 ℃．第一イオン化エネルギー733.2 kJ mol^－1(7.60 eV)．高温で酸素と反応して三酸化物WO₃になる．フッ素と室温で反応して六フッ化物WF₆をつくる．塩素とも容易に反応して六塩化物となる．酸化数1～6．通常の酸，希アルカリ水溶液には侵されない．常温で水と反応しない．
金属は白熱電球，蛍光灯のフィラメント，電子管，ブラウン管の電極，X線管のターゲットなどに用いられる．鋼との合金や炭化タングステンは超硬合金として高速切削用工具，強力・耐蝕合金ハステロイはNi，Cr，Moとの合金，タングステン酸カルシウムは蛍光灯用の蛍光体，硫化タングステンは高温用の潤滑剤に用いられる．[CAS 7440-33-7]

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