technetium

Japanese: テクネチウム

Tc. An element with atomic number 43. An artificial radioactive element. It is a transition element in the fifth row of the seventh group of the periodic table with the electron configuration [Kr]4d ⁵ 5s ^2. Currently, isotopes of technetium are known with mass numbers from 85 to 118. It was predicted by DI Mendeleev as ecamanganese. In 1925, W. Noddack and I. Tacke reported the discovery of element 43 in uranium minerals from the X-ray fluorescence spectrum, and named it masurium after Noddack's hometown, Masuria, but this was not accepted. In 1937, C. Perrier and E. Segré synthesized the first confirmed element 43 by bombarding molybdenum with accelerated deuterons in a cyclotron at the University of California, Berkeley. The search for Tc on Earth continued, and in 1962, PK Kuroda and BT Kenna confirmed its presence in trace amounts in uranium ore from Gabon, Africa, as a spontaneous fission product of uranium. Its presence is also inferred from its spectral lines in S, M, and N type stars. A recent detailed reexamination of the X-ray spectrum by Nodak et al. revealed that they had also found Tc. As the first artificially created element, Segré et al. named it technetium, from the Greek word τεχνητο (technètos), meaning "man-made." ⁹⁹ Tc is a relatively stable β ^- decay nuclide with a half-life of 2.11×10 ⁵ y, and exists in large quantities as a fission product in spent uranium fuel from nuclear reactors. ^99m Tc, currently widely used in medicine, is a nuclide that emits 0.143 MeV gamma rays with a half-life of 6.0058 h and is obtained as a daughter nuclide of ⁹⁹ Mo. ^95m Tc, with a half-life of 61 d, is also used as a tracer. It is a silver-gray, hexagonal close-packed metal. Its melting point is 2172 °C, its boiling point is 4877 °C, its density is 11.5 g cm ^-3 (calculated value at 20 °C). It is superconducting below 7.8 K. Its first ionization energy is 7.28 eV. The metal is obtained by reduction of ammonium pertechnetate with hydrogen. It is soluble in nitric acid, aqua regia, and concentrated sulfuric acid, but insoluble in hydrochloric acid. The oxidation states 2 to 7.7 are the most stable, and various salts are formed as pertechnetate (tetraoxotechnetium(VII) acid ion), TcO ₄ ^- . Known forms include fluorides TcF ₅ and TcF ₆ , chlorides TcCl ₄ and TcCl ₆ , and bromide TcBr ₄ . The oxide Tc ₂ O ₇ has a melting point of 119.5°C and a boiling point of 310.6°C, making it quite volatile. [CAS 7440-26-8][CAS 14133-76-7: ⁹⁹ Tc][CAS 12165-21-8:Tc ₂ O ₇ ]

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

Japanese:

Tc．原子番号43の元素．人工放射性元素．電子配置[Kr]4d⁵5s²の周期表7族第5周期遷移元素．テクネチウムの同位体は現在，質量数85～118まで知られている．D.I. Mendeleev(メンデレーエフ)がエカマンガンとして予言していた元素．1925年にW. Noddack(ノダック)とI. Tackeがウラン鉱物中にX線蛍光スペクトルから43番元素を発見したと報告し，ノダックの故郷の地名Masuriaにちなんでマスリウムと命名したが受け入れられず，1937年にC. PerrierとE. Segréがカリフォルニア大学バークレー校のサイクロトロンで，加速した重陽子でモリブデンを衝撃して合成したものが，確認された最初の43番元素．その後も地球上のTcの探索が続けられ，1962年に至り，P.K. Kuroda(黒田和夫)とB.T. Kennaがアフリカ・ガボン産のせんウラン鉱中に，ウランの自発核分裂生成物として微量の存在を確認した．S，M，N型星にもスペクトル線から存在が推定される．最近，ノダックらのX線スペクトルを詳細に再検討したところ，かれらもTcを見つけていたことが判明した．はじめて人工的につくられた元素として，Segréたちが“人造の”を意味するギリシア語τεχνητο(technètos)からtechnetiumと命名した．⁹⁹Tc は，半減期2.11×10⁵ y の比較的安定な β^－崩壊核種で，原子炉使用済みウラン燃料中に核分裂生成物として多量に存在する．現在，医学の分野で広く利用されている ^99mTc は，半減期6.0058 h で0.143 MeV のγ線を放出する核種で，⁹⁹Mo の娘核種として得られる．半減期61 d の ^95mTc もトレーサーとして使用される．銀灰色の六方最密金属．融点2172 ℃，沸点4877 ℃．密度11.5 g cm^－3(20 ℃ 計算値)．7.8 K 以下で超伝導を示す．第一イオン化エネルギー7.28 eV．金属は過テクネチウム酸アンモニウムの水素による還元で得られる．硝酸，王水，濃硫酸に可溶，塩酸に不溶．酸化数2～7．7がもっとも安定で過テクネチウム酸(テトラオキソテクネチウム(Ⅶ)酸イオン)TcO₄^－として種々の塩をつくる．フッ化物TcF₅，TcF₆，塩化物TcCl₄，TcCl₆，臭化物TcBr₄などが知られる．酸化物中Tc₂O₇は融点119.5 ℃，沸点310.6 ℃ でかなり揮発性である．[CAS 7440-26-8][CAS 14133-76-7:⁹⁹Tc][CAS 12165-21-8:Tc₂O₇]