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hydrogen

[ hahy-druh-juhn ]

noun

  1. a colorless, odorless, flammable gas that combines chemically with oxygen to form water: the lightest of the known elements. : H; : 1.00797; : 1; density: 0.0899 grams/liter at 0°C and 760 millimeters pressure.


hydrogen

/ ˈhaɪdrɪdʒən /

noun

    1. a flammable colourless gas that is the lightest and most abundant element in the universe. It occurs mainly in water and in most organic compounds and is used in the production of ammonia and other chemicals, in the hydrogenation of fats and oils, and in welding. Symbol: H; atomic no: 1; atomic wt: 1.00794; valency: 1; density: 0.08988 kg/m³; melting pt: –259.34°C; boiling pt: –252.87°C See also deuterium tritium
    2. ( as modifier )

      hydrogen bomb



hydrogen

/ drə-jən /

  1. 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 H 2 . 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.
  2. See Periodic Table See Note at oxygen


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Word History and Origins

Origin of hydrogen1

First recorded in 1785–95; from the French word hydrogène; hydro- 1, -gen

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Word History and Origins

Origin of hydrogen1

C18: from French hydrogène, from hydro- + -gen ; so called because its combustion produces water

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Compare Meanings

How does hydrogen compare to similar and commonly confused words? Explore the most common comparisons:

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Example Sentences

That’s because plastics are mainly made up of carbon and hydrogen, very widespread elements.

Making renewable hydrogen requires making electricity to send a charge through water to split the liquid into hydrogen and oxygen.

There, a chemical process breaks the bond between water’s hydrogen and oxygen molecules, forming heat.

To begin, the scientists shined X-ray light on hydrogen gas.

Polyethylene is a long molecule, in which hydrogen atoms are connected to a carbon backbone that can be thousands of carbon atoms long.

Methane (chemical formula CH4) is one of the simplest hydrocarbons, which literally means “containing hydrogen and carbon.”

From that, they extracted the ratio of the number of deuterium atoms to the number of hydrogen atoms.

They found that there are roughly 1,900 hydrogen atoms for each deuterium atom in the water on Comet 67P.

Deuterium is an isotope of hydrogen containing a proton and neutron in its nucleus, while normal hydrogen has only a proton.

Jupiter and its cousins, by contrast, are mostly made of hydrogen and hydrogen compounds.

Hydrogen sulphid is easily prepared in the simple apparatus shown in Fig. 30.

It is allowed to cool, and hydrogen sulphid gas is passed through it for about five minutes.

Ammonia is a compound of nitrogen and hydrogen, but it cannot be formed by the direct union of these gases.

One morning he found that the amount of hydrogen was scarcely perceptible; still there was water in the pit.

The older workman reassured them; the carbon was much heavier than oxygen, and even thicker than hydrogen.

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