tellurium

Te. Atomic number 52. Nonmetallic element in group 16 of the periodic table with electron configuration [Kr]4d ¹⁰ 5s ² 5p ^4. Atomic weight 127.60(3). Isotopes with mass numbers between 105 and 132 are known, of which eight are stable: 120, 122-126, 128 (31.74(8)%), and 130 (34.08(62)%); the rest are radioactive. Tellurium was isolated from gold ore by FJ Müller of Austria in 1782. It was confirmed by MH Klaproth, who named the element after tellus, the Roman goddess of the earth, in 1798. The Japanese name for the element comes from the German name Tellur. In his book "Shamitsu Kaisyu" published in 1837, Udagawa Yoan refers to it as Tellurium.
Abundance in the earth's crust: 0.01 ppm (average elemental abundance up to a depth of 20 miles). It is the least abundant of all chalcogens, existing as telluride in sulfides, etc. It is obtained as a by-product of electrolytic refining of copper, lead, etc. It is a brittle silvery-white semimetal of the hexagonal crystal system. Its melting point is 449.5 °C, its boiling point is 990 °C. Its density is 6.24 g cm ^-3 (20 °C). Its oxidation states are -2, 4, and 6. Its first ionization energy is 9.009 eV. When telluric acid (telluric acid (IV) H ₂ TeO ₃ ) is reduced with sulfur dioxide, it gives off a gray amorphous form of tellurium. It does not react with water, but is slowly oxidized in air, and when heated, it gives off a blue flame and turns into TeO _2. It is insoluble in hydrochloric acid and dilute sulfuric acid, but soluble in oxidizing acids, aqua regia, and sodium hydroxide solution. Tellurium is similar to sulfur and selenium, but is more metallic and basic; it is an amphoteric substance. It is not as reactive as sulfur or selenium, but in concentrated alkaline solutions it forms tellurides and tellurite, and when made acidic, tellurium precipitates. There are many compounds that correspond to sulfur and selenium, but telluric acid H ₆ TeO ₆ is a weaker acid than sulfuric acid or selenic acid. Tellurium reacts with active metals to form tellurides, which are similar to sulfides, but are less stable than sulfides. It does not react with hydrogen, but reacts directly with halogens to form halides. It forms compounds with an oxidation number of -2 with electropositive elements, and with electropositive elements with oxidation numbers of 2, 4, and 6. It can also form polycations such as Te ₄ ²⁺ and Te ₆ ²⁺ .
Adding small amounts (0.01-1%) to steel, stainless steel, etc. improves mechanical workability and toughness. Also used as a glass pigment, catalyst, and rubber vulcanization accelerator. TeGeSb alloys and GeSbTeBi alloys are used as optical recording media such as CD-R, CD-RW, and DVD, while Cd-Te alloys are used in solar cells. Toxic to the human body, "tellurium and its compounds" are designated as Type 2 chemical substances under the PRTR Law. Work environment Class 2 (gas 1 mg/ ^m3 or less, particulate matter 0.1 mg/ ^m3 or less). Dangerous and harmful substances requiring notification of names, etc. under the Industrial Safety and Health Law. [CAS 13494-80-9][See other terms] Tellurides

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

Te．原子番号52の元素．電子配置[Kr]4d¹⁰5s²5p⁴の周期表16族非金属元素．原子量127.60(3)．質量数105～132の同位体が知られているが，120，122～126，128(31.74(8)％)，130(34.08(62)％)の8種が安定で，それ以外は放射性同位体である．1782年オーストリアのF.J. Müllerが金鉱石からテルルを分離した．確認はM.H. Klaprothで，元素名は1798年にかれがローマ神話の“地球の女神”tellusにちなんで命名した．日本語の元素名はドイツ語の元素名Tellurから．宇田川榕菴は天保8年(1837年)に出版した「舎密開宗」で，的爾律母(テルリュリュウム)としている．
地殻中の存在度0.01 ppm(深度20マイルまでの平均元素存在度)．カルコゲン中で存在量は最少で，硫化物中にテルル化物などとして存在する．銅，鉛などの電解精錬の副産物として得られる．六方晶系に属する銀白色のもろい半金属．融点449.5 ℃，沸点990 ℃．密度6.24 g cm^－3(20 ℃)．酸化数－2，4，6．第一イオン化エネルギー9.009 eV．亜テルル酸(テルル(Ⅳ)酸H₂TeO₃)を二酸化硫黄で還元すると灰色の無定形テルルが得られる．水とは反応しないが，空気中で徐々に酸化され，熱すると青い炎をあげてTeO₂になる．塩酸，希硫酸に不溶，酸化力のある酸，王水，水酸化ナトリウム溶液に可溶．テルルは硫黄，セレンに似ているが，より金属的で塩基性も示す両性物質である．硫黄やセレンほど反応性は高くないが，濃アルカリ溶液でテルル化物と亜テルル酸塩となり，酸性にするとテルルが析出する．硫黄やセレンに相当する化合物が多いが，テルル酸H₆TeO₆は硫酸やセレン酸に比較して弱酸である．テルルは活性金属との反応により硫化物に似たテルル化物をつくるが，硫化物より不安定である．水素とは反応しないが，ハロゲンとは直接反応してハロゲン化物をつくる．陽性元素とは－2の酸化数の，陰性元素とは2，4，6の酸化数の化合物をつくる．また，Te₄^2＋，Te₆^2＋ などのポリ陽イオンもできる．
鋼，ステンレススチールなどへの少量(0.01～1％)の添加は機械的加工性，強靭性を改善する．ガラスの顔料や触媒，ゴム加硫促進剤としても用いられる．TeGeSb合金，GeSbTeBi合金などは光記録媒体としてCD-R，CD-RW，DVDなどに，Cd-Te合金は太陽電池に用いられる．人体に有毒で，「テルル及びその化合物」はPRTR法・第二種指定化学物質．作業環境クラス2(気体1 mg/m³ 以下，粒子状物質0.1 mg/m³ 以下)．労働安全衛生法の名称等を通知すべき危険物及び有害物．[CAS 13494-80-9][別用語参照]テルル化物

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