helium
helium
[ˈhiːlɪəm]
noun
[ˈhiːlɪəm]
noun
- [mass noun]the chemical element of atomic number 2, an inert gas which is the lightest member of the noble gas series(Symbol: He)
氦（符号：He） - Helium occurs in traces in air, and more abundantly in natural gas deposits. It is used as a lifting gas for balloons and airships, and liquid helium (boiling point: 4.2 kelvins, -268.9°C) is used as a coolant. Helium is produced in stars as the main product of the thermonuclear fusion of hydrogen, and is the second most abundant element in the universe after hydrogen
- late 19th cent.: modern Latin, from Greek hēlios 'sun', because its existence was inferred from an emission line in the sun's spectrum
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