名詞 protactinium:

1. a short-lived radioactive metallic element formed from uranium and disintegrating into actinium and then into lead
   同義詞：protoactinium, Pa, atomic number 91

pro.tac.tin.i.um

n.Symbol Pa （名詞）符號(hào) Pa
A rare, extremely toxic, radioactive element chemically similar to uranium, having 3 known isotopes, the most common of which is protactinium 23 with a half-life of 32,480 years. Atomic number 9; melting point ,230=C; specific gravity 5.37; valence 4, 5.See table at element
鏷：一種稀有的、劇毒放射性元素，在化學(xué)性質(zhì)上與鈾相似。有十三個(gè)已知的同位素，其中最常見的是半衰期為32,480年的鏷23。原子序數(shù)為9；熔點(diǎn),230=C；比重5.37；原子價(jià)4, 5參見 element

來源：
prot(o)-
prot(o)-
actinium [so called because it disintegrates into actinium]
actinium [它被這樣取名是由于它分裂成錒]