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hy·dro·gen 
Audio Help [hahy-druh-juhn] Pronunciation Key
Audio Help [hahy-druh-juhn] Pronunciation Key –noun
| a colorless, odorless, flammable gas that combines chemically with oxygen to form water: the lightest of the known elements. Symbol: H; atomic weight: 1.00797; atomic number: 1; density: 0.0899 g/l at 0°C and 760 mm pressure. |
| Dictionary.com Unabridged (v 1.1) Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006. |
hydrogen
To learn more about hydrogen visit Britannica.com
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| hy·dro·gen
Audio Help (hī'drə-jən) Pronunciation Key
n. Symbol H A colorless, highly flammable gaseous element, the lightest of all gases and the most abundant element in the universe, used in the production of synthetic ammonia and methanol, in petroleum refining, in the hydrogenation of organic materials, as a reducing atmosphere, in oxyhydrogen torches, and in rocket fuels. Atomic number 1; atomic weight 1.00794; melting point -259.14°C; boiling point -252.8°C; density at 0°C 0.08987 gram per liter; valence 1. See Table at element. [French hydrogène : Greek hudro-, hydro- + French -gène, -gen.] hy·drog'e·nous (-drōj'ə-nəs) adj. |
| The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2006 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved. |
hydrogen
1791, from Fr. hydrogène, coined 1787 by G. de Morveau from Gk. hydr-, stem of hydros "water" + Fr. -gène "producing." So called because it forms water when exposed to oxygen. Hydrogen bomb first recorded 1947; shortened form H-bomb is from 1950.
| Online Etymology Dictionary, © 2001 Douglas Harper |
| hydrogen | |
noun | |
| a nonmetallic univalent element that is normally a colorless and odorless highly flammable diatomic gas; the simplest and lightest and most abundant element in the universe |
| WordNet® 3.0, © 2006 by Princeton University. |
hydrogen [ˈhaidrədʒən] noun
an element, the lightest gas, which burns and which, when combined with oxygen, produces water
See also: hydrogen bomb
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| Kernerman English Multilingual Dictionary (Beta Version), © 2000-2006 K Dictionaries Ltd. |
| hydrogen
Audio Help (hī'drə-jən) Pronunciation Key
Symbol H The lightest and most abundant element in the universe, normally consisting of one proton and one electron. It occurs in water in combination with oxygen, in most organic compounds, and in small amounts in the atmosphere as a gaseous mixture of its three isotopes (protium, deuterium, and tritium) in the colorless, odorless compound H2. Hydrogen atoms are relatively electropositive and form hydrogen bonds with electronegative atoms. In the Sun and other stars, the conversion of hydrogen into helium by nuclear fusion produces heat and light. Hydrogen is used to make rocket fuel, synthetic ammonia, and methanol, to hydrogenate fats and oils, and to refine petroleum. The development of physical theories of electron orbitals in hydrogen was important in the development of quantum mechanics. Atomic number 1; atomic weight 1.00794; melting point -259.14°C; boiling point -252.8°C; density at 0°C 0.08987 gram per liter; valence 1. See Periodic Table. See Note at oxygen. |
| The American Heritage® Science Dictionary Copyright © 2002 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved. |
hydrogen
The lightest chemical element; its symbol is H. Hydrogen normally consists of a single electron in orbit around a nucleus made up of a single proton. It is usually found as a gas and has several uses as a fuel.
Note: Hydrogen atoms are combined to form helium atoms in fusion reactions in stars and in hydrogen bombs, which release huge amounts of energy. Hydrogen also burns rapidly, producing water as it combines with oxygen (see H8O and oxidation).
Note: For a time, hydrogen was frequently used to fill blimps and dirigibles because of its extremely low weight. In 1937, however, the hydrogen in the dirigible Hindenburg caught fire, and many of the passengers and crew were killed. Since that time, helium has been widely preferred to hydrogen for use in airships; it is not as buoyant (see buoyancy) or cheap as hydrogen, but, being an inert gas, it does not burn.
Note: Because there is so much hydrogen in stars, it is by far the most abundant element in the universe.
[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. |
hy·dro·gen (h
dr
-jn)
n.
Symbol H
- A colorless, highly flammable gaseous element, the most abundant in the universe, used in ammonia and methanol synthesis, in the hydrogenation of organic materials, and as a reducing atmosphere. Atomic number 1; atomic weight 1.00797; melting point -259.34°C; boiling point -252.9°C; density at 0°C 0.08988 gram per liter; valence 1.
| The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company. |
Main Entry: hy·dro·gen
Pronunciation: 'hI-dr&-j&n
Function: noun
: a nonmetallic element that is the simplest and lightest of the
elements and that is normally a colorless odorless highly flammable diatomic gas —symbol H; —see DEUTERIUM,
TRITIUM, ELEMENT table
—hy·drog·e·nous /hI-'dräj-&-n&s/ adjective
| Merriam-Webster's Medical Dictionary, © 2002 Merriam-Webster, Inc. |
Hydrogen
Hy"dric\, a. [From Hydrogen.] (Chem.) Pertaining to, or containing, hydrogen; as, hydric oxide. Hydric dioxide. (Chem.) See Hydrogen dioxide, under Hydrogen. Hydric oxide (Chem.), water. Hydric sulphate (Chem.), hydrogen sulphate or sulphuric acid.| Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc. |
Hydrogen
Hy"dric\, a. [From Hydrogen.] (Chem.) Pertaining to, or containing, hydrogen; as, hydric oxide. Hydric dioxide. (Chem.) See Hydrogen dioxide, under Hydrogen. Hydric oxide (Chem.), water. Hydric sulphate (Chem.), hydrogen sulphate or sulphuric acid.| Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc. |
Hydrogen
Hy"dro*gen\, n. [Hydro-, 1 + -gen: cf. F. hydrog[`e]ne. So called because water is generated by its combustion. See Hydra.] (Chem.) A gaseous element, colorless, tasteless, and odorless, the lightest known substance, being fourteen and a half times lighter than air (hence its use in filling balloons), and over eleven thousand times lighter than water. It is very abundant, being an ingredient of water and of many other substances, especially those of animal or vegetable origin. It may by produced in many ways, but is chiefly obtained by the action of acids (as sulphuric) on metals, as zinc, iron, etc. It is very inflammable, and is an ingredient of coal gas and water gas. It is standard of chemical equivalents or combining weights, and also of valence, being the typical monad. Symbol H. Atomic weight 1. Note: Although a gas, hydrogen is chemically similar to the metals in its nature, having the properties of a weak base. It is, in all acids, the base which is replaced by metals and basic radicals to form salts. Like all other gases, it is condensed by great cold and pressure to a liquid which freezes and solidifies by its own evaporation. It is absorbed in large quantities by certain metals (esp. palladium), forming alloy-like compounds; hence, in view of quasi-metallic nature, it is sometimes called hydrogenium. It is the typical reducing agent, as opposed to oxidizers, as oxygen, chlorine, etc. Bicarbureted hydrogen, an old name for ethylene. Carbureted hydrogen gas. See under Carbureted. Hydrogen dioxide, a thick, colorless liquid, H2O2, resembling water, but having a bitter, sour taste, produced by the action of acids on barium peroxide. It decomposes into water and oxygen, and is manufactured in large quantities for an oxidizing and bleaching agent. Called also oxygenated water. Hydrogen oxide, a chemical name for water, H?O. Hydrogen sulphide, a colorless inflammable gas, H2S, having the characteristic odor of bad eggs, and found in many mineral springs. It is produced by the action of acids on metallic sulphides, and is an important chemical reagent. Called also sulphureted hydrogen.| Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc. |
Hydrogen
Hy`dro*ge"ni*um\, n. [NL. See Hydrogen.] (Chem.) Hydrogen; -- called also in view of its supposed metallic nature. --Graham.| Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc. |
Hydrogen
Hy*drog"u*ret\, n. [From Hydrogen.] (Chem.) A hydride. [Obs.]| Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc. |
Hydrogen
Sul"phide\, n. (Chem.) A binary compound of sulphur, or one so regarded; -- formerly called sulphuret. Double sulphide (Chem.), a compound of two sulphides. Hydrogen sulphide. (Chem.) See under Hydrogen. Metallic sulphide, a binary compound of sulphur with a metal.| Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc. |
Hydrogen
Sul"phu*ret`ed\, a. (Chem.) Combined or impregnated with sulphur; sulphurized. [Written also sulphuretted.] Sulphureted hydrogen. (Chem.) See Hydrogen sulphide, under Hydrogen.| Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc. |
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