protactinium
noun/ˌprəʊtækˈtɪniəm/
/ˌprəʊtækˈtɪniəm/
[uncountable] (symbol Pa)
- a chemical element. Protactinium is a radioactive metal found naturally when uranium decays .Word Originearly 20th cent.: from proto- ‘original, earlier’ + actinium, so named because one of its isotopes decays to form actinium.
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protactinium