| 释义 |
ra·di·um AHD[rāʹdē-əm] D.J.[ˈreɪdiːəm]K.K.[ˈrediəm]n.Symbol Ra （名词）符号 Ra - 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
- Latin radius [ray] 拉丁语 radius [射线]
- -ium -ium
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