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. 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

/ hī′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

Word History and Origins

Origin of hydrogen¹

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

Word History and Origins

Origin of hydrogen¹

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

Example Sentences

Those fuels today are based on food waste and farm crops, although alternatives including hydrogen lie on the horizon.

From Los Angeles Times

The UK government confirmed support for two electrolytic hydrogen projects in Wales, in Milford Haven and Bridgend, to support low carbon hydrogen production.

From BBC

But now this bioluminescent algae is dying and releasing hydrogen sulfide gas, which causes a rotten egg smell, explained Laura Rink, associate director at Heal the Bay Aquarium in Santa Monica.

From Los Angeles Times

Fewer than 2% are zero-emission, and they include 332 electric trucks and 51 hydrogen fuel cell trucks.

From Los Angeles Times

In the longer term, new technologies such as hydrogen power and electrification are likely to play a role, at least on shorter routes.

From BBC