Hydrogen anion

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Hydrogen anion
CAS number 12184-88-2
PubChem 166653
ChemSpider 145831 YesY
Gmelin Reference 14911
Jmol-3D images Image 1
Molecular formula H
Molar mass 1.00794 g mol−1
Std molar
108.96 J K−1 mol−1
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

The hydrogen anion is a negative ion of hydrogen, H. The hydrogen anion is an important constituent of the atmosphere of stars, such as the Sun. In chemistry, this ion is called hydride.


The hydrogen anion is the dominant absorber of photons in the interstellar medium. It absorbs energies in the range 0.75–4.0 eV, which ranges from the infrared into the visible spectrum (Rau 1999, Srinivasan 1999). It also occurs in the Earth's ionosphere (Rau 1999).

Its existence was first proven theoretically by Hans Bethe in 1929 (Bethe 1929). H is unusual because, in its free form, it has no bound excited states, as was finally proven in 1977 (Hill 1977). It has been studied experimentally using particle accelerators (Bryant 1977).

In chemistry, the hydride anion is hydrogen that has the oxidation state −1. Hydride compounds formally contain a hydrogen anion. Most such compounds are in fact rather covalent. An example of a hydride is borohydride (BH

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  1. ^ "Hydride - PubChem Public Chemical Database". The PubChem Project. USA: National Center for Biotechnology Information.