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Hasil cari dari kata atau frase: Helium (0.01081 detik)
Found 2 items, similar to Helium.
English → English (WordNet)
Definition: helium
helium
n : a very light colorless element that is one of the six inert
gasses; the most difficult gas to liquefy; occurs in
economically extractable amounts in certain natural gases
(as those found in Texas and Kansas) [syn:
He,
atomic number 2
]
English → English (gcide)
Definition: Helium
Helium
\He"li*um\ (h[=e]"l[i^]*[u^]m), 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. It is obtained from natural gas in industrial
quantities. Symbol, He; atomic number 2; at. wt., 4.0026
(C=12.011). 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 is an inert noble gas, belonging to the argon group, and
cannot be made to form compounds. The helium nucleus is the
charged particle which constitutes alpha rays, and helium is
therefore formed as a decomposition product of certain
radioactive substances such as radium. The normal helium
nucleus has two protons and two neutrons, but an isotope with
only one neutron is also observed in atmospheric helium at an
abundance of 0.013 %. Liquid helium has a boiling point of
-268.9[deg] C at atmospheric pressure, and is used for
maintaining very low temperatures, both in laboratory
experimentation and in commercial applications to maintain
superconductivity in low-temperature superconducting devices.
Gaseous helium at normal temperatures is used for buoyancy in
blimps, dirigibles, and high-altitude balloons, and also for
amusement in party balloons.
[Webster 1913 Suppl. +PJC]
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