| 单词 | rubidium |
| 释义 | Word Frequency rubidium(ruːˈbɪdɪəm) noun a soft highly reactive radioactive element of the alkali metal group; the 16th most abundant element in the earth's crust (310 parts per million), occurring principally in pollucite, carnallite, and lepidolite. It is used in electronic valves, photocells, and special glass. Symbol: Rb; atomic no: 37; atomic wt: 85.4678; half-life of87Rb: 5 × 1011 years; valency: 1, 2, 3, or 4; relative density: 1.532 (solid), 1.475 (liquid); melting pt: 39.48°C; boiling pt: 688°C Derived forms rubidic (ruˈbidic) adjective Word origin C19: from New Latin, from Latin rubidus dark red, with reference to the two red lines in its spectrum |
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