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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Isotopes of strontium ： ウィキペディア英語版 Isotopes of strontium The alkaline earth metal strontium (Sr) has four stable, naturally occurring isotopes: 84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%). It has a standard atomic mass of 87.62(1) u. Only 87Sr is radiogenic; it is produced by decay from the radioactive alkali metal 87Rb, which has a half-life of 4.88 × 1010 years. Thus, there are two sources of 87Sr in any material: primordial that formed during nucleosynthesis along with 84Sr, 86Sr and 88Sr, as well as that formed by radioactive decay of 87Rb. The ratio 87Sr/86Sr is the parameter typically reported in geologic investigations; ratios in minerals and rocks have values ranging from about 0.7 to greater than 4.0. Because strontium has an electron configuration similar to that of calcium, it readily substitutes for Ca in minerals. Thirty-one unstable isotopes are known to exist, the longest-lived of which are 90Sr with a half-life of 28.9 years and 85Sr with a half-life of 64.853 days. Of importance are strontium-89 (89Sr) with a half-life of 50.57 days, and strontium-90 (90Sr). They decay by emitting an electron and an antineutrino ($\backslash bar\_e$) in beta decay (β− decay) to become yttrium: :$\backslash mathrm^\_Sr\}\backslash rightarrow\backslash mathrm^\_Y\}\; +\; e^-\; +\; \backslash bar\_e$ :$\backslash mathrm^\_Sr\}\backslash rightarrow\backslash mathrm^\_Y\}\; +\; e^-\; +\; \backslash bar\_e$ 89Sr is an artificial radioisotope used in treatment of bone cancer. In circumstances where cancer patients have widespread and painful bony metastases, the administration of 89Sr results in the delivery of beta particles directly to the area of bony problem, where calcium turnover is greatest. 90Sr is a by-product of nuclear fission found in nuclear fallout and presents a health problem since it substitutes for calcium in bone, preventing expulsion from the body. Because it is a long-lived high-energy beta emitter, it is used in SNAP (Systems for Nuclear Auxiliary Power) devices. These devices hold promise for use in spacecraft, remote weather stations, navigational buoys, etc., where a lightweight, long-lived, nuclear-electric power source is required. The 1986 Chernobyl nuclear accident contaminated a vast area with 90Sr. The lightest isotope is 73Sr and the heaviest being 107Sr. All other isotopes have half-lives shorter than 55 days, most under 100 minutes. == Table == 〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Isotopes of strontium」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.