Word Study
actinium
CIDE DICTIONARY
actinium, n. [Gr. , , ray.].
A supposed metal, said by Phipson to be contained in commercial zinc; -- so called because certain of its compounds are darkened by exposure to light. [1913 Webster]
OXFORD DICTIONARY
actinium, n. Chem. a radioactive metallic element of the actinide series, occurring naturally in pitchblende.
Usage
Symb.: Ac.
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