- an unstable radioactive element of the alkali-metal group, occurring in minute amounts in uranium ores. Symbol: Fr; atomic no: 87; half-life of most stable isotope, 223Fr: 22 minutes; valency: 1; melting pt: 27°C; boiling pt: 677°C
| 单词 | francium |
| 释义 | WordReference Random House Unabridged Dictionary of American English © 2024 fran•ci•um (fran′sē əm),USA pronunciation n. [Chem.]
Collins Concise English Dictionary © HarperCollins Publishers:: francium /ˈfrænsɪəm/ n
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