osmium

Japanese: オスミウム

Os. Element with atomic number 76. A precious metal element in group ⁸ (platinum group) of the periodic table with the electron configuration [Xe] ^4f145d66s2 . The element's name comes from the Greek οσμη (osmè) ^, meaning "odor," because its volatile oxide has a pungent odor. Udagawa Yoan called it osmè in his book Shami Kaisō, published in 1837. It was discovered in platinum ores by the British scientist S. Tennant in 1803. Atomic weight 190.23(3). Seven stable isotopes with mass numbers 184 (0.02(1)%), 186 (1.59(3)%), 187 (1.96(2)%), 188 (13.24(8)%), 189 (16.15(5)%), 190 (26.26(2)%), and 192 (40.78(19)%) are known, as well as radioactive isotopes with mass numbers from 162 to 197 and 199.
In nature, it occurs as an alloy with iridium in platinum ore. In the old rectangular periodic table, Os, Ir, and Pt are in Group Ⅷ and have similar properties, so it is difficult to separate them from each other. The metal is obtained by reducing the oxide with hydrogen. Osmium catalysts are obtained by adsorbing osmium salts onto a support and reducing them. It is difficult to process, so it is usually sintered before use. It has a melting point of 3054 °C, a boiling point of 5027 °C, and a first ionization energy of 8.28 eV. It has a density of 22.59 g cm ^-3 (20 °C), making it the densest substance. Mohs hardness is 7.5. Its usual oxidation numbers are 2 (d ⁶ ) and 3 (d ⁵ ), but compounds with oxidation numbers 0 to 8 are known, excluding 1. It is the most easily oxidized of the platinum group elements, and at high temperatures it also reacts with fluorine and chlorine. It reacts with carbon monoxide to produce carbonyl compounds from Os ⁰ (CO) ₅ to Os ₈ (CO) ₂₃ . Soluble in hot concentrated sulfuric acid, concentrated nitric acid, sodium hypochlorite, and molten alkali hydrogen sulfate. Used for filaments due to its high melting point, and for pen tips due to its corrosion and abrasion resistance. Initially used as a catalyst for hydrogenation and ammonia synthesis (Haber-Bosch process). _OsO4 is used as an oxidation catalyst for olefins. [CAS 7440-04-2]

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

Japanese:

Os．原子番号76の元素．電子配置[Xe]4f¹⁴5d⁶6s²の周期表8族(白金族)貴金属元素．元素名は揮発性の酸化物が刺激臭をもつためギリシア語の“臭”を意味するοσμη(osmè)から命名された．宇田川榕菴は天保8年(1837年)に出版した「舎密開宗」で阿斯繆母(ヲスミュム)としている．1803年イギリスのS. Tennantが白金鉱中に発見した．原子量190.23(3)．質量数184(0.02(1)％)，186(1.59(3)％)，187(1.96(2)％)，188(13.24(8)％)，189(16.15(5)％)，190(26.26(2)％)，192(40.78(19)％)の7種の安定同位体と，質量数162～197，199の放射性同位体が知られている．
天然には，白金鉱中にイリジウムとの合金として産出する．矩周期型の昔の周期表では，Os，Ir，PtはⅧ族で性質は類似するため，相互分離は困難である．金属は酸化物を水素で還元すると得られる．オスミウム触媒は担体にオスミウム塩を吸着させ還元すると得られる．加工が困難で，普通は焼結して利用する．融点3054 ℃，沸点5027 ℃，第一イオン化エネルギー8.28 eV．密度22.59 g cm^－3(20 ℃)で，物質中最大の密度をもつ．モース硬さ7.5．通常の酸化数は2(d⁶)，3(d⁵)であるが，1を除いて0から8の化合物が知られている．白金族元素のなかでもっとも酸化されやすく，高温ではフッ素，塩素とも反応する．一酸化炭素と反応してOs⁰ (CO)₅からOs₈(CO)₂₃までのカルボニル化合物を生じる．熱濃硫酸，濃硝酸，次亜塩素酸ナトリウム，融解硫酸水素アルカリに可溶．融点の高いことを利用してフィラメントに，耐食性，耐摩耗性を利用してペン先に用いる．水素添加，アンモニア合成(ハーバー-ボッシュ法)にも当初は触媒として用いられた．OsO₄はオレフィンの酸化触媒として使われる．[CAS 7440-04-2]