ra.di.um
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 3 isotopes with mass numbers between 23 and 230, of which radium 22' with a half-life of ,'22 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 ,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3种同位素，质量数介于23和230之间，最常见的为镭22'，半衰期为,'22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,737=C；原子价2参见 element
来源：Latin radius [ray] 拉丁语 radius [射线] -ium -ium
