| 单词 | francium |
| 释义 | Word Frequency francium(ˈfrænsɪəm) noun 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 Word origin C20: from New Latin, from France + -ium; so-called because first found in France |
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