| 单词 | helium |
| 释义 | helium /hee"lee euhm/, n. an inert, gaseous element present in the sun's atmosphere and in natural gas, and also occurring as a radioactive decomposition product, used as a substitute for flammable gases in dirigible balloons. Symbol: He; at. wt.: 4.0026; at. no.: 2; density: 0.1785 g/l at 0°C and 760 mm pressure. [1875-80; < NL < Gk héli(os) the sun + NL -ium -IUM] |
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