samarium

Japanese: サマリウム

Sm. Atomic number 62. Electron configuration [Xe] ^4f66s2 . Lanthanide element in group ³ of the periodic table. A member of the cerium group of rare earth elements. Atomic weight 150.36(2). Seven naturally occurring isotopes are known: mass numbers 144 (3.07(7)%), 147 (14.99(18)%), 148 (11.24(10)%), 149 (13.82(7)%), 150 (7.38(1)%), 152 (26.75(16)%), and 154 (22.75(29)%). There is also a radioactive isotope with mass number 128. Of the naturally occurring isotopes, ¹⁴⁶ Sm, ¹⁴⁷ Sm, and ¹⁴⁸ Sm are alpha emitters with half-lives of 1.03×10 ⁸ y, 1.06×10 ¹¹ y, and 7×10 ¹⁵ y, respectively. It was isolated from samarskite by L. de Boisbaudran in 1879, after which it was named. It is found in samarskite, gadolinite, and cercite. Its abundance in the earth's crust is 3.5 ppm. The metal obtained by electrolysis of molten chloride salts is silvery white. Its melting point is 1077 °C, its boiling point is 1791 °C, its density is 7.52 g cm ^-3 (20 °C). Its boiling point is similar to that of Eu, and significantly lower than that of other lanthanides (> 3000 °C). Standard electrode potential Sm ³⁺ /Sm-2.30 V. First ionization energy is 5.644 eV. Soluble in dilute acid. Also reacts with hot water. There are compounds with oxidation numbers 2 and 3, but Sm ^III compounds have the same properties as other rare earth elements. The compound is yellow in color and has the weakest paramagnetism of the rare earth elements. The electron configurations of Sm ²⁺ and Sm ³⁺ are 4f ⁶ and 4f ⁵ . Sm ^II compounds are similar to Yb ^II and Ba ^II compounds, and the sulfates and phosphates are poorly soluble in water. They are easily oxidized in aqueous solutions and are more unstable than Eu ^II compounds. Their main use is in heat-resistant permanent magnets and samarium-cobalt magnets (SmCo ₅ , Sm ₂ Co ₁₇ , Sm ₂ (Co,Fe,Cu,Zr)). In the 1980s, they were widely used in headphones such as the Walkman, but were replaced by cheaper and more powerful Nd-Fe-B magnets. They are still sometimes used in mobile phones. [CAS 7440-19-9]

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

Japanese:

Sm．原子番号62の元素．電子配置[Xe]4f⁶6s²の周期表3族ランタノイド元素．希土類元素セリウム族の一つ．原子量150.36(2)．質量数144(3.07(7)％)，147(14.99(18)％)，148(11.24(10)％)，149(13.82(7)％)，150(7.38(1)％)，152(26.75(16)％)，154(22.75(29)％)の7種の天然に存在する同位体と，質量数128の放射性同位体が知られている．天然に存在する同位体のうち，¹⁴⁶Sm，¹⁴⁷Sm，¹⁴⁸Sm はそれぞれ，半減期1.03×10⁸ y，1.06×10¹¹ y，7×10¹⁵ y のα放射体である．1879年，L.de Boisbaudranによりサマルスキー石から分離された．元素名はサマルスキー石にちなんで命名された．サマルスキー石，ガドリン石，セル石に含まれる．地殻中の存在度3.5 ppm．塩化物の溶融塩電解により得られる金属は銀白色．融点1077 ℃，沸点1791 ℃．密度7.52 g cm^－3(20 ℃)．沸点はEuと同様，ほかのランタノイド元素( ＞ 3000 ℃)よりいちじるしく低い．標準電極電位 Sm^3＋/Sm－2.30 V．第一イオン化エネルギー5.644 eV．希酸に可溶．熱水とも反応する．酸化数2，3の化合物があるが，Sm^Ⅲの化合物はほかの希土類元素と同様の性質をもつ．化合物の色は黄色で常磁性は希土類元素中もっとも弱い．Sm^2＋，Sm^3＋の電子配置は4f⁶，4f⁵．Sm^Ⅱの化合物は，Yb^Ⅱ，Ba^Ⅱの化合物に類似し，硫酸塩，リン酸塩は水に難溶．水溶液中で容易に酸化され，Eu^Ⅱ化合物より不安定である．耐熱性永久磁石，サマリウム-コバルト磁石(SmCo₅，Sm₂Co₁₇，Sm₂(Co,Fe,Cu,Zr))用が最大の用途である．1980年代にはウォークマンなどヘッドフォンに多用されたが，より安価で強力なNd-Fe-B磁石にとってかわられた．携帯電話用にはまだ使われることもある．[CAS 7440-19-9]