| 释义 |
WordReference Random House Unabridged Dictionary of American English © 2024ac•tin•i•um (ak tin′ē əm),USA pronunciation n. [Chem.]- Chemistrya radioactive silver-white metallic element that glows blue in the dark, resembling the rare earths in chemical behavior and valence. Symbol: Ac;
at. no.: 89;
at. wt.: 227.
Collins Concise English Dictionary © HarperCollins Publishers:: actinium /ækˈtɪnɪəm/ n - a radioactive element of the actinide series, occurring as a decay product of uranium. It is used as an alpha-particle source and in neutron production. Symbol: Ac; atomic no: 89; half-life of most stable isotope,227Ac: 21.6 years; relative density: 10.07; melting pt: 1051°C; boiling pt: 3200 ± 300°C
Etymology: 19th Century: New Latin, from actino- + -ium |