Hydrogen anion

Hydrogen anion

Names
Systematic IUPAC name Hydride[1]
Identifiers
CAS Number	12184-88-2
3D model (JSmol)	Interactive image
ChEBI	CHEBI:29239
ChemSpider	145831 Y
Gmelin Reference	14911
PubChem CID	166653
CompTox Dashboard (EPA)	DTXSID6075306
InChI InChI=1S/H/q-1 Y Key: KLGZELKXQMTEMM-UHFFFAOYSA-N Y
SMILES [H-]
Properties
Chemical formula	H−
Molar mass	1.009 g·mol−1
Conjugate acid	Dihydrogen
Thermochemistry
Std molar entropy (S⦵298)	108.96 J K−1 mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

The hydrogen anion, H⁻, is a negative ion of hydrogen, that is, a hydrogen atom that has captured an extra electron. The hydrogen anion is an important constituent of the atmosphere of stars, such as the Sun. In chemistry, this ion is called hydride. The ion has two electrons bound by the electromagnetic force to a nucleus containing one proton.

The binding energy of H⁻ equals the binding energy of an extra electron to a hydrogen atom, called electron affinity of hydrogen. It is measured to be 0.754195(19) eV or 0.0277161(62) hartree (see Electron affinity (data page)). The total ground state energy thus becomes −14.359888 eV.