| 单词 | 质量数 |
| 释义 | 〔radium〕A rare, brilliant white, luminescent, highly radioactive metallic element found in very small amounts in uranium ores, having 13 isotopes with mass numbers between 213 and 230, of which radium 226 with a half-life of 1,622 years is the most common. It is used in cancer radiotherapy, as a neutron source for some research purposes, and as a constituent of luminescent paints. Atomic number 88; melting point 700°C; boiling point 1,737°C; valence 2. See table at element 镭：一种稀有的、有白色光泽、发光、高度放射性的金属元素，极少量地存在于沥青矿中，有13种同位素，质量数介于213和230之间，最常见的为镭226，半衰期为1,622年。镭可用于癌症的放射治疗，在其它一些研究中用作中子源，还可用作发光颜料的成分。原子序数88；熔点700°C；沸点1,737°C；原子价2 参见 element〔isotope〕One of two or more atoms having the same atomic number but different mass numbers.同位素：两个或更多具有相同原子序数却具有不同的质量数的原子中的一个〔mendelevium〕A synthetic radioactive transuranium element of the actinide series. Atomic number 101; mass numbers 255 and 256; half-lives approximately 30 minutes (Md 255) and 1.5 hours (Md 256). See table at element 钔：锕系之合成放射性超铀元素。其原子序数为101；质量数为255和256；半衰期大约为30分钟（质量数为255的元素），及一个半小时（质量数为256的元素） 参见 element〔radiothorium〕A radioactive isotope of thorium with mass number 228.射钍：钍的放射性同位，质量数为228〔polonium〕A naturally radioactive metallic element, occurring in minute quantities as a product of radium disintegration and produced by bombarding bismuth or lead with neutrons. It has 27 isotopes ranging in mass number from 192 to 218, of which Po 210, with a half-life of 138.39 days, is the most readily available. Atomic number 84; melting point 254°C; boiling point 962°C; specific gravity 9.32; valence 2, 4. See table at element 钋：一种具有天然辐射性的金属元素，作为镭分裂的产物以极小量出现，可通过用中子轰击铋或铅获得。它从192到218的质量数中可排列为27种同位素，其中的钋210半衰期达138.39天，是最易得到的同位素。原子序数84；熔点254°C；沸点962°C；比重9.32；化合价2, 4 参见 element〔promethium〕A radioactive rare-earth element prepared by fission of uranium or by neutron bombardment of neodymium, having 14 isotopes with mass numbers ranging from 141 to 154 and used as a source of beta rays. Atomic number 61; melting point 1,168°C; boiling point 2,460°C; valence 3. See table at element 钜：放射性稀土元素，由铀分裂或钛的中子爆炸而成，有十四个拥有从141到154的质量数的同位素，用作β射线源。原子序数61；熔点1,168°C；沸点2,460°C；原子价为3 参见 element |
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