holmium

Ho. Atomic number 67. Element in group 3 of the periodic table with electron configuration [Xe]4f ¹¹ 6s ^2. One of the rarest rare earth elements in the yttrium group. Atomic weight 164.93032(2). A mononuclear element with only one stable isotope, mass 165 (100%). Radioactive isotopes with mass numbers between 140 and 175 are known. It was discovered by JL Soret of France through spectral analysis in 1878, and was discovered independently by PT Cleve of Sweden. Cleve named it after Holmia, the Latin name for Stockholm.
It is found in euxenite and gadolinite. Its abundance in the earth's crust is 0.78 ppm. It is a silvery-white metal. It has a hexagonal close-packed structure. Its melting point is 1474 °C, its boiling point is 2695 °C. Its density is 8.795 g cm ^-3 (25 °C). Its first ionization energy is 6.022 eV. It dissolves in hot water and acid, producing hydrogen. Its compounds and ions are yellow in colour. Its oxidation number is 3. Its chemical properties are similar to those of other rare earth elements, with its fluorides, carbonates and oxalates being insoluble in water. Its compounds are paramagnetic, and, along with dysprosium compounds, it has the largest magnetic moment of any rare earth element. The electron configuration of Ho ³⁺ is 4f ¹⁰ .
The oxides are used as glass colorants and capacitor materials, Ho:YAG is used in 2 μm band laser crystals for medical applications, and _HoCu2 is used as a cold storage material for small refrigerators. [CAS 7440-60-0]

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

Ho．原子番号67の元素．電子配置[Xe]4f ¹¹6s²の周期表3族ランタノイド元素．もっとも希少の希土類元素イットリウム族の一つ．原子量164.93032(2)．安定同位体核種が質量数165(100％)のみの単核種元素．質量数140～175の放射性同位体が知られている．1878年，フランスのJ-L. Soretがスペクトル分析で見いだし，独立にスウェーデンのP.T. Cleve(クレーベ)により発見された．ストックホルムのラテン名HolmiaによりCleveが命名．
ユークセン石，ガドリン石などに含まれる．地殻中の存在度0.78 ppm．銀白色金属．六方最密構造．融点1474 ℃，沸点2695 ℃．密度8.795 g cm^－3(25 ℃)．第一イオン化エネルギー6.022 eV．熱水，酸に溶けて水素を発生する．化合物，イオンの色は黄色．酸化数3．化学的性質はほかの希土類元素と同様で，フッ化物，炭酸塩，シュウ酸塩などが水に不溶．化合物は常磁性で，ジスプロシウム化合物とともに希土類中もっとも大きい磁気能率を示す．Ho^3＋ の電子配置は4f ¹⁰．
酸化物は，ガラス着色剤，コンデンサー用材料に，Ho：YAGは医療用などに用いられる2 μm 帯のレーザー結晶に，HoCu₂は小型冷凍機用蓄冷材に用いられる．[CAS 7440-60-0]

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