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Chemical, physical and material properties and data of the chemical element Hydrogen.



Hydrogen - chemical symbol H (from hydrogenium = water former), atomic number 1 - is a gaseous, colorless and odorless chemical element from the element group of the nonmetals. Natural isotopes of hydrogen are protium, deuterium and tritium.

Hydrogen is in many respects an element of superlatives: As the first basic element of matter, it is listed in the periodic table; at the same time, according to current knowledge - apart from small amounts of helium - it was the only element that existed in the universe after the Big Bang; all other basic chemical building blocks were only formed later by nuclear synthesis in the stars. To this day, hydrogen is the most common of the chemical elements in the entire universe.

Hydrogen is the lightest element; on earth, under normal conditions, it is a combustible gas made up of dihydrogen molecules H2, which means that two hydrogen atoms are connected to one another by a chemical bond: H-H. While in space most of the hydrogen occurs unbound, the terrestrial deposits are predominantly bound in hydrogen-containing chemical compounds, of which water - chemically dihydrogen oxide - is the best known. For example, free hydrogen is released into the atmosphere during volcanic eruptions.


General Information about Hydrogen

Regular nameHydrogenChemical symbolHOther namesElement 1Systematic nameHistorical namesHydrogeniumName meaning, originLatin: Hydrogenium = water-formerDiscovery (year)(1766) - Henry CavendishOccurenceHydrogen is the most common chemical elementPosition in the PSEGroup 1, period 1, s-block, main group IGroup membershipNonmetal


Atomar Properties of Hydrogen

Atomic number Z1 = number of protonsStandard Atomic Weight1.008
intervall: [1.00784, 1.00811]


Electron configuration of Hydrogen


Abbreviated form: 1s1.


Ionization Energies of Hydrogen

The following table lists the ionization energies IE (ionization potentials); the IE is the energy required in electron volts (eV) per atom to separate a given electron from an Hydrogen atom.



Isotopic Data of Hydrogen

An overview of the nuclides as well as the isotopic data and properties are listed on the following page: Hydrogen isotopes.


Chemistry of Hydrogen


Valence electrons1Oxidation states+ 1. - 1Electronegativity2.1 (Pauling original)
2.20 (Pauling)
2.300 (Allen)
2.8 (Mulliken)
2.31 (Sanderson)
2.20 (Allred-Rochow)
7.1862 eV (Gosh Gupta)
7.18 eV (Pearson)
Electron affinity0.754 195(19) eV
72.769(2) kJ mol-1


Standard Electrode Potential

E0 (V)SymbolNoxName Ox.
Name Red.
- I
Hydride anion
H2 (g)
⇄ 2 H-
+ 2 e-
-0.8277H+ I
2 H2O (l)
⇄ H2 (g) + 2 OH-
+ 2 e-
0H+ I
2 H+
⇄ H2 (g)
+ 2 e-


Material and Physical Properties

Melting point- 259.16 °CEnthalpy of fusion (molar)0.117 kJ mol-1Boiling point- 252.879 °CEnthalpy of vaporization0.46 kJ mol-1Density0.08988 g L -1 (0°C; 101.325 kPa. H2)


External Data, Identifiers

CAS registry number1333-74-0InChI =1S/HInChIKeyUFHFLCQGNIYNRP-UHFFFAOYSA-NPubChem ID783


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Last update: 2022-12-20

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