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.
Abbreviated form: 1s1.
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.
An overview of the nuclides as well as the isotopic data and properties are listed on the following page: Hydrogen isotopes.
|E0 (V)||Symbol||Nox||Name Ox.|
⇄ 2 H-
|+ 2 e-|
|2 H2O (l)|
⇄ H2 (g) + 2 OH-
|+ 2 e-|
⇄ H2 (g)
|+ 2 e-|
Last update: 2022-12-20
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