plutonium

Pu. An element with atomic number 94. An artificial radioactive transuranium element. It is an actinide element in group 3 of the periodic table with the electron configuration [Rn]5f ⁶ 7s ^2. Twenty isotope species with mass numbers between 228 and 247 are known. In 1940, GT Seaborg's group bombarded uranium ²³⁸ U with deuterium nuclei D ⁺ accelerated in the 60 in cyclotron at the University of California, Berkeley, to obtain a nuclide with mass number 238, as follows: ²³⁸ U(d, 2n) ²³⁸ Np β decay → ²³⁸ Pu. It was named after Pluto, following uranium (Uranus) and neptunium (Neptune).
²⁴⁴ Pu has the longest life, with a half-life of 8.00×10 ⁷ y (α decay). The most important ²³⁹ Pu has a half-life of 2.411×10 ⁴ y (α decay). When ²³⁸ U is irradiated with neutrons, it decays through two β decays.

²³⁸ U→ ²³⁹ U→ ²³⁹ Np→ ²³⁹ Pu
It is obtained as follows. The alpha particle energy is 5.155-5.105 MeV. It also undergoes spontaneous fission with a branching rate of 3×10 ^-10 %. Approximately 200 kg is produced per year from ²³⁸ U in a 1 million kW power reactor. The critical mass for fission varies depending on the degree of compression, but it is said to be around 10 kg without a reflector, and a nuclear warhead carries 2-4 kg of weapons-grade plutonium (93% ²³⁹ Pu). It is a silvery-white metal. It is very heavy, with a density of 19.84 g cm ^-3 (alpha state 25 °C). Its melting point is 641 °C, and its boiling point is 3232 °C. Its first ionization energy is 5.8 eV. It is paramagnetic. The metal shows complex crystal structure transitions, with a total of six transformations. α (monoclinic system) below 122 °C, β (body-centered monoclinic) 122-200 °C, γ (orthorhombic system) 200-310 °C, δ (face-centered cubic structure) 310-452 °C, δ' (tetragonal system) 452-480 °C, ε (body-centered cubic structure) above 480 °C. Thermal and electrical conductivity is not high. Specific resistance 145 μΩ cm. The metal is obtained by reducing PuF ₄ , PuO ₂ , and PuCl ₃ with alkaline earth metals such as Ca. Soluble in concentrated hydrochloric acid, dilute sulfuric acid, and perchloric acid. Oxidation states 2-7 are known, with the most stable oxidation state being 4. PuH ₂ , PuO, etc. have been reported to have an oxidation state of 2. Compounds with higher oxidation numbers are more easily hydrolyzed and more susceptible to redox reactions due to the alpha rays they emit. Insoluble in water except for halides and nitrates. The aqueous solutions take on vivid colors depending on the oxidation state. Known colors include Pu ^III (blue-purple), Pu ^IV (yellow-brown), Pu ^V O ₂ ⁺ (pink), Pu ^VI O ₂ ^{2 +} (pink-orange), Pu ^VII O ₅ ^{3 -} (blue), PuF ₃ (purple), PuF ₄ (reddish-brown), PuF ₆ (reddish-brown), other halides, PuO, PuO ₂ (yellow-brown), Pu ₂ O ₃ (black), sulfides, and nitrides.
Both the metal and its compounds are toxic, damaging organs such as the bones and lungs. However, the risk of radiation damage is far greater than its toxicity as a heavy metal. The airborne concentration limit for ²³⁹ Pu compounds other than insoluble oxides is 7 x 10 ^-7 Bq/cm ³ , and the concentration limit in wastewater is 4 x 10 ^-3 Bq/cm ³ (Radiation Hazard Prevention Ordinance - stipulating the quantity of isotopes, etc.). It is used in nuclear weapons and nuclear fuel. ²³⁸ Pu (alpha decay, half-life 87.7 years) is used in nuclear batteries for space. It was also used in the Apollo lunar exploration missions, and in pacemakers implanted in the human body. [CAS 7440-07-5][CAS 13842-83-6:PuF ₃ ][CAS 13709-56-3:PuF ₄ ][CAS 13693-06-6:PuF ₆ ][CAS 12035-83-5:PuO][CAS 12059-95-9:PuO ₂ ][CAS 12036-34-9: _{Pu2O3 ]}

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

Pu．原子番号94の元素．人工放射性超ウラン元素．電子配置[Rn]5f ⁶7s²の周期表3族アクチノイド元素．質量数228～247の20種の同位体核種が知られている．1940年に，G.T. Seaborg(シーボーグ)グループがカリフォルニア大学バークレー校の60 in サイクロトロンで加速した重水素核 D^＋ でウラン ²³⁸U を衝撃して，²³⁸U(d，2n)²³⁸Np β崩壊→ ²³⁸Pu のように質量数238の核種を得た．ウラン天王星，ネプツニウム海王星についで冥王星(プルトー)から命名された．
²⁴⁴Pu がもっとも長寿命で半減期8.00×10⁷ y(α崩壊)．もっとも重要な ²³⁹Pu は半減期2.411×10⁴ y(α崩壊)．²³⁸U の中性子照射により，2回のβ崩壊を経て

²³⁸U→ ²³⁹U→ ²³⁹Np→ ²³⁹Pu
のようにして得られる．α粒子エネルギーは5.155～5.105 MeV．分岐率3×10^－10 ％ で自発核分裂も起こす．100万kW 級発電炉1基で ²³⁸U から年間約200 kg 生成する．核分裂に対する臨界質量は圧縮度でも異なるが，反射体なしで10 kg 程度，核弾頭には2～4 kg の兵器級プルトニウム(93％ ²³⁹Pu)を搭載しているといわれる．銀白色の金属．密度19.84 g cm^－3(α態25 ℃)で非常に重い．融点641 ℃，沸点3232 ℃．第一イオン化エネルギー5.8 eV．常磁性．金属は複雑な結晶構造転移を示し，合計六つの変態がある．α(単斜晶系)122 ℃ 以下，β(体心単斜)122～200 ℃，γ(斜方晶系)200～310 ℃，δ(面心立方構造)310～452 ℃，δ′(正方晶系)452～480 ℃，ε(体心立方構造)480 ℃ 以上．熱伝導性，電気伝導性は高くはない．比抵抗145 μΩ cm．金属はPuF₄，PuO₂，PuCl₃をCaなどのアルカリ土類金属で還元すると得られる．濃塩酸，希硫酸，過塩素酸に可溶．酸化数2～7の酸化状態が知られ，もっとも安定な酸化状態は4．酸化数2はPuH₂，PuOなどが報じられている．高酸化数の化合物ほど加水分解しやすく，自己の放出するα線で酸化還元反応を受けやすい．ハロゲン化物，硝酸塩以外は水に難溶．水溶液は酸化数に応じて，鮮やかな色を帯びる．Pu^Ⅲ(青紫色)，Pu^Ⅳ(黄褐色)，Pu^Ⅴ O₂^＋(桃色)，Pu^Ⅵ O₂^2＋(桃橙色)，Pu^Ⅶ O₅^3－(青色)，PuF₃(紫色)，PuF₄(赤褐色)，PuF₆(赤褐色)，ほかのハロゲン化物，PuO，PuO₂(黄褐色)，Pu₂O₃(黒色)，硫化物，窒化物などが知られる．
金属および化合物ともに有毒で骨，肺などの臓器に障害を与える．ただし，重金属としての毒性よりも放射能障害の可能性のほうがはるかに高い．不溶性の酸化物以外の ²³⁹Pu 化合物の空気中濃度限度7×10^－7 Bq/cm³，排水中の濃度限度4×10^－3 Bq/cm³(放射線障害防止令・同位元素の数量等を定める件)．用途は核兵器および核燃料用．²³⁸Pu(α崩壊，半減期87.7 y)は宇宙用原子力電池に使われる．かつて月面探査のアポロ計画や人体に埋め込むペースメーカー用にも使用された．[CAS 7440-07-5][CAS 13842-83-6:PuF₃][CAS 13709-56-3:PuF₄][CAS 13693-06-6:PuF₆][CAS 12035-83-5:PuO][CAS 12059-95-9:PuO₂][CAS 12036-34-9:Pu₂O₃]

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