| 释义 |
WordReference Random House Learner's Dictionary of American English © 2024he•li•um /ˈhiliəm/USA pronunciation n. [uncountable]- Chemistryan inert, gaseous element present in natural gas.
See -helio-. WordReference Random House Unabridged Dictionary of American English © 2024he•li•um (hē′lē əm),USA pronunciation n. - Chemistryan 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.
- Greek hé̄li(os) the sun + Neo-Latin -ium -ium
- Neo-Latin
- 1875–80
Collins Concise English Dictionary © HarperCollins Publishers:: helium /ˈhiːlɪəm/ n - a very light nonflammable colourless odourless element that is an inert gas, occurring in certain natural gases: used in balloons and in cryogenic research. Symbol: He; atomic no: 2; atomic wt: 4.002602; density: 0.1785 kg/m³; at normal pressures it is liquid down to absolute zero; melting pt: below –272.2°C; boiling pt: –268.90°C
Etymology: 19th Century: New Latin, from helio- + -ium; named from its having first been detected in the solar spectrum |