Hydrogen

HH 2 hydrogen gasmolecular hydrogendihydrogenhydrogen moleculeH + gaseous hydrogenH 3 H 5
Hydrogen is the chemical element with the symbol H and atomic number 1.wikipedia
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Chemical element

elementelementschemical elements
Hydrogen is the chemical element with the symbol H and atomic number 1.
The two lightest elements, hydrogen and helium, were mostly formed in the Big Bang and are the most common elements in the universe.

Star

starsstellarmassive star
Hydrogen is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass. Non-remnant stars are mainly composed of hydrogen in the plasma state.
For at least a portion of its life, a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star's interior and then radiates into outer space.

Periodic table

periodic table of elementsperiodic table of the elementsperiodic system
With a standard atomic weight of 1.008, hydrogen is the lightest element in the periodic table.
The elements from atomic numbers 1 (hydrogen) through 118 (oganesson) have been discovered or synthesized, completing seven full rows of the periodic table.

Symbol (chemistry)

symbolchemical symbolchemical symbols
Hydrogen is the chemical element with the symbol H and atomic number 1.

Universe

physical worldThe Universeuniverses
Hydrogen is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass. Non-remnant stars are mainly composed of hydrogen in the plasma state.
Giant clouds of hydrogen and helium were gradually drawn to the places where dark matter was most dense, forming the first galaxies, stars, and everything else seen today.

Proton

protonsH + p
The most common isotope of hydrogen, termed protium (name rarely used, symbol 1 H), has one proton and no neutrons.
In previous years, Rutherford had discovered that the hydrogen nucleus (known to be the lightest nucleus) could be extracted from the nuclei of nitrogen by atomic collisions.

Abundance of the chemical elements

abundanceabundancesabundant
Hydrogen is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass. Non-remnant stars are mainly composed of hydrogen in the plasma state.
As another example, looking at the mass-fraction abundance of hydrogen and helium in both the Universe as a whole and in the atmospheres of gas-giant planets such as Jupiter, it is 74% for hydrogen and 23–25% for helium; while the (atomic) mole-fraction for hydrogen is 92%, and for helium is 8%, in these environments.

Neutron

neutronsfree neutronn
The most common isotope of hydrogen, termed protium (name rarely used, symbol 1 H), has one proton and no neutrons.
Neutrons are required for the stability of nuclei, with the exception of the single-proton hydrogen atom.

Water

H 2 OHOliquid water
Since hydrogen readily forms covalent compounds with most nonmetallic elements, most of the hydrogen on Earth exists in molecular forms such as water or organic compounds.
Its chemical formula is H 2 O, meaning that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds.

Taste

sourbittergustatory
At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, highly combustible diatomic gas with the molecular formula H 2.
Saltiness and sourness are perceived when alkali metal or hydrogen ions enter taste buds, respectively.

Big Bang

Big Bang theoryThe Big Bangbig-bang
The universal emergence of atomic hydrogen first occurred during the recombination epoch (Big Bang).
Giant clouds of these primordial elements (mostly hydrogen, with some helium and lithium) later coalesced through gravity, eventually forming early stars and galaxies, the descendants of which are visible today.

Hydrogen production

production of hydrogenproduce hydrogenproduction
Industrial production is mainly from steam reforming natural gas, and less often from more energy-intensive methods such as the electrolysis of water.
Hydrogen production is the family of industrial methods for generating hydrogen.

Nonmetal

non-metalReactive nonmetalnon-metals
At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, highly combustible diatomic gas with the molecular formula H 2.
The elements generally classified as nonmetals include one element in group 1 (hydrogen); one in group 14 (carbon); two in group 15 (nitrogen and phosphorus); three in group 16 (oxygen, sulfur and selenium); most of group 17 (fluorine, chlorine, bromine and iodine); and all of group 18 (with the possible exception of oganesson).

Ammonia

NH 3 anhydrous ammonialiquid ammonia
Most hydrogen is used near the site of its production, the two largest uses being fossil fuel processing (e.g., hydrocracking) and ammonia production, mostly for the fertilizer market.
Ammonia is a compound of nitrogen and hydrogen with the formula NH 3.

Henry Cavendish

CavendishCavendish balanceCavendish, Henry
In 1766–81, Henry Cavendish was the first to recognize that hydrogen gas was a discrete substance, and that it produces water when burned, the property for which it was later named: in Greek, hydrogen means "water-former".
He is noted for his discovery of hydrogen, which he termed "inflammable air".

Electrolysis of water

water electrolysiselectrolysiselectrolyzer
Industrial production is mainly from steam reforming natural gas, and less often from more energy-intensive methods such as the electrolysis of water.
Electrolysis of water is the decomposition of water into oxygen and hydrogen gas due to the passage of an electric current.

Hydrogen embrittlement

embrittlementembrittleembrittle metals
Hydrogen is problematic in metallurgy because it can embrittle many metals, complicating the design of pipelines and storage tanks.
Hydrogen embrittlement (HE) also known as hydrogen assisted cracking (HAC) and hydrogen-induced cracking (HIC), describes the embrittling of metal after being exposed to hydrogen.

Recombination (cosmology)

recombinationrecombination epochCosmic Decoupling
The universal emergence of atomic hydrogen first occurred during the recombination epoch (Big Bang).
In cosmology, recombination refers to the epoch at which charged electrons and protons first became bound to form electrically neutral hydrogen atoms.

Combustion

burningignitionincomplete combustion
At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, highly combustible diatomic gas with the molecular formula H 2.
A simple example can be seen in the combustion of hydrogen and oxygen into water vapor, a reaction commonly used to fuel rocket engines.

Isotopes of hydrogen

protiumhydrogen-1 1 H
Hydrogen gas (dihydrogen or molecular hydrogen, also called diprotium when consisting specifically of a pair of protium atoms) is highly flammable:
Hydrogen ( 1 H) has three naturally occurring isotopes, sometimes denoted 1 H, 2 H, and 3 H. The first two of these are stable, while 3 H has a half-life of 12.32 years.

Oxyhydrogen

oxy-hydrogenOxyhydrogen flameKnallgas
Pure hydrogen-oxygen flames emit ultraviolet light and with high oxygen mix are nearly invisible to the naked eye, as illustrated by the faint plume of the Space Shuttle Main Engine, compared to the highly visible plume of a Space Shuttle Solid Rocket Booster, which uses an ammonium perchlorate composite.
Oxyhydrogen is a mixture of hydrogen (H 2 ) and oxygen (O 2 ) gases.

Fossil fuel

fossil fuelsoil and gasOil & Gas
Most hydrogen is used near the site of its production, the two largest uses being fossil fuel processing (e.g., hydrocracking) and ammonia production, mostly for the fertilizer market.
Fossil fuels range from volatile materials with low carbon-to-hydrogen ratios (like methane), to liquids (like petroleum), to nonvolatile materials composed of almost pure carbon, like anthracite coal.

Covalent bond

covalentcovalentlycovalently bonded
Since hydrogen readily forms covalent compounds with most nonmetallic elements, most of the hydrogen on Earth exists in molecular forms such as water or organic compounds.
In the molecule, the hydrogen atoms share the two electrons via covalent bonding.

Gas

gasesgaseousgaseous state
At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, highly combustible diatomic gas with the molecular formula H 2.
The only chemical elements that are stable diatomic homonuclear molecules at STP are hydrogen (H 2 ), nitrogen (N 2 ), oxygen (O 2 ), and two halogens: fluorine (F 2 ) and chlorine (Cl 2 ).

Hydrogen chloride

HClanhydrous hydrochloric acidHCl gas
Hydrogen can react spontaneously and violently at room temperature with chlorine and fluorine to form the corresponding hydrogen halides, hydrogen chloride and hydrogen fluoride, which are also potentially dangerous acids.
Hydrogen chloride is a diatomic molecule, consisting of a hydrogen atom H and a chlorine atom Cl connected by a polar covalent bond.