hydrogen

American  

[hahy-druh-juhn] / ˈhaɪ drə dʒən /

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 British  

/ 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 Scientific  

/ 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

---

Etymology

Origin of hydrogen

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

Compare meaning

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

• hydrogen vs. atomic bomb
• deuterium vs. hydrogen

Example Sentences

In addition to electrical attraction, the mineral forms chemical bonds and hydrogen bonds that create strong links between its surface and organic molecules.

From Science Daily

These toxic elements sat in the channel’s then-stagnant water, which led to a die-off of all vegetation and the emission of foul-smelling hydrogen sulfide.

From Los Angeles Times

Rabi at the 1954 hearing convened to consider stripping J. Robert Oppenheimer of his security clearance because of his opposition to developing the hydrogen bomb.

From Los Angeles Times

Berlin has now accelerated efforts to lessen its reliance on American LNG and wants to increasingly bank on green hydrogen generated through clean energy to achieve its climate targets.

From Barron's

The two-day test included filling the Space Launch System rocket with propellants, liquid hydrogen and liquid oxygen.

From Barron's