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he·li·um 
Audio Help [hee-lee-uhm] Pronunciation Key
Audio Help [hee-lee-uhm] Pronunciation Key –noun
| 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; atomic weight: 4.0026; atomic number: 2; density: 0.1785 g/l at 0°C and 760 mm pressure. |
li(os) the sun + NL -ium | Dictionary.com Unabridged (v 1.1) Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006. |
helium
To learn more about helium visit Britannica.com
| © 2008 Encyclopædia Britannica, Inc. |
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helium I
–noun
| colorless liquid helium existing below its boiling point of 4.2 K and above the lambda point of 2.186 K. |
| Dictionary.com Unabridged (v 1.1) Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006. |
helium II
–noun
| liquid helium existing as a superfluid below the lambda point of 2.186 K, having very low viscosity and very high thermal conductivity. |
| Dictionary.com Unabridged (v 1.1) Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006. |
| he·li·um
Audio Help (hē'lē-əm) Pronunciation Key
n. Symbol He A colorless, odorless inert gaseous element occurring in natural gas and with radioactive ores. It is used as a component of artificial atmospheres and laser media, as a refrigerant, as a lifting gas for balloons, and as a superfluid in cryogenic research. Atomic number 2; atomic weight 4.0026; boiling point -268.9°C; density at 0°C 0.1785 gram per liter. See Table at element. [From Greek hēlios, sun (so called because its existence was deduced from the solar spectrum); see sāwel- in Indo-European roots.] |
| The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2006 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved. |
helium
1868, coined from Gk. helios "sun" (see sol), because the element was observed in the solar spectrum during the eclipse of Aug. 18, 1868, by Eng. astronomer Sir Joseph N. Lockyer (1836-1920) and Eng. chemist Sir Edward Frankland (1825-99). It was not actually obtained until 1895.
| Online Etymology Dictionary, © 2001 Douglas Harper |
| helium | |
noun | |
| 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) |
| WordNet® 3.0, © 2006 by Princeton University. |
helium [ˈhiːliəm] noun
an element, a very light gas which does not burn and which is used eg in balloons
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| Kernerman English Multilingual Dictionary, © 2000-2006 K Dictionaries Ltd. |
| helium
Audio Help (hē'lē-əm) Pronunciation Key
Symbol He A very lightweight, colorless, odorless element in the noble gas group. Helium occurs in natural gas, in radioactive ores, and in small amounts in the atmosphere. It has the lowest boiling point of any substance and is the second most abundant element in the universe. Helium is used to provide lift for balloons and blimps and to create artificial air that will not react chemically. Atomic number 2; atomic weight 4.0026; boiling point -268.9°C; density at 0°C 0.1785 gram per liter. See Periodic Table. Our Living Language : The second most abundant element in the universe after hydrogen, Helium (symbol He) is a colorless, odorless, nonmetallic gas that is produced abundantly by the nuclear fusion in all stars and is found in smaller amounts on Earth. It was discovered by the British scientist—and founding editor of the journal Nature—Joseph Norman Lockyer in 1868, while he was studying a solar eclipse with a spectroscope, an instrument that breaks light up into a spectrum. If an element is heated up enough to glow, the emitted light produces a unique spectrum when refracted through a prism. Lockyer noticed that the spectrum of the Sun's corona, which is visible only during a solar eclipse, contained lines produced by an unknown element. He named the element helium from helios, the Greek word for "sun." Helios gives us many other words pertaining to the Sun, such as heliocentric and perihelion. |
| The American Heritage® Science Dictionary Copyright © 2002 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved. |
helium
A chemical element, usually found in the form of a gas, in which two electrons are in orbit, and the nucleus consists of two protons and two neutrons. Its symbol is He.
Note: Helium is the best known of the inert gases.
Note: Because it is lighter than air, helium is used to fill balloons.
[Chapter:] Physical Sciences and Mathematics
| The American Heritage® New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved. |
Helium
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.| Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc. |
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. 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.| Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc. |
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