He"li*um (hē"l&ibreve;*ŭm), n. [NL., fr. Gr. "h`lios the sun.]
(Chem.) An inert, monoatomic, gaseous element occurring in the atmosphere of the sun and stars, and in small quantities in the earth's atmosphere, in several minerals and in certain mineral waters. Symbol, He; at. wt., 4. Helium was first detected spectroscopically in
the sun by
Lockyer in 1868; it was first prepared by Ramsay in 1895. Helium has a density
of 1.98 compared with hydrogen, and is more difficult to liquefy than the latter. Chemically, it belongs to the argon
group and cannot be made to form
compounds. It is a decomposition product of the radium emanation.
He"li*um (?), n. [NL.,
fr. Gr. &?; the sun.]
(Chem.) A gaseous
element found in the atmospheres of the sun and earth and
in some rare minerals.
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