| 释义 |
pro·tac·tin·i·um AHD[prō'tăk-tĭnʹē-əm] D.J.[ˌprəʊtækˈtɪniːəm]K.K.[ˌprotækˈtɪniəm]n.Symbol Pa （名词）符号 Pa - A rare, extremely toxic, radioactive element chemically similar to uranium, having 13 known isotopes, the most common of which is protactinium 231 with a half-life of 32,480 years. Atomic number 91; melting point 1,230°C; specific gravity 15.37; valence 4, 5. See table at element 镤：一种稀有的、剧毒放射性元素，在化学性质上与铀相似。有十三个已知的同位素，其中最常见的是半衰期为32,480年的镤231。原子序数为91；熔点1,230°C；比重15.37；原子价4, 5 参见 element
- prot(o)- prot(o)-
- actinium [so called because it disintegrates into actinium] actinium [它被这样取名是由于它分裂成锕]
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