Helium hydride ion

Helium hydride ion
Names
	Systematic IUPAC name Hydridohelium(1+)
	Other names Helonium; Helium hydride
Identifiers
CAS Number	13766-24-0 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:33688; CHEBI:33689 neutral excimer;
ChemSpider	21106447 ;
Gmelin Reference	2
CompTox Dashboard (EPA)	DTXSID801018818 ;
	InChI InChI=1S/HHe/h1H/q+1 Key: HSFAAVLNFOAYQX-UHFFFAOYSA-N ;
	SMILES [HeH+];
Properties
Chemical formula	HeH+;
Molar mass	5.01054 g·mol−1
Conjugate base	Helium
Related compounds
Related compounds	Neonium, Argonium, Kryptonium, Xenonium
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

The helium hydride ion, hydridohelium(1+) ion, or helonium is a cation (positively charged ion) with chemical formula HeH⁺. It consists of a helium atom bonded to a hydrogen atom, with one electron removed. It can also be viewed as protonated helium. It is the lightest heteronuclear ion, and is believed to be the first compound formed in the Universe after the Big Bang.^[3]

The ion was first produced in a laboratory in 1925. It is stable in isolation, but extremely reactive, and cannot be prepared in bulk, because it would react with any other molecule with which it came into contact. Noted as the strongest known acid—stronger than even fluoroantimonic acid—its occurrence in the interstellar medium had been conjectured since the 1970s,^[4] and it was finally detected in April 2019 using the airborne SOFIA telescope.^[5]^[6]

^ "hydridohelium(1+) (CHEBI:33688)". Chemical Entities of Biological Interest (ChEBI). European Bioinformatics Institute.
^ "Helium hydride". American Chemical Society.
^ Cite error: The named reference EngelEtAl was invoked but never defined (see the help page).
^ "Hydridohelium (CHEBI:33689)". Chemical Entities of Biological Interest (ChEBI). European Bioinformatics Institute.
^ Güsten, Rolf; Wiesemeyer, Helmut; Neufeld, David; Menten, Karl M.; Graf, Urs U.; Jacobs, Karl; Klein, Bernd; Ricken, Oliver; Risacher, Christophe; Stutzki, Jürgen (April 2019). "Astrophysical detection of the helium hydride ion HeH⁺". Nature. 568 (7752): 357–359. arXiv:1904.09581. Bibcode:2019Natur.568..357G. doi:10.1038/s41586-019-1090-x. PMID 30996316. S2CID 119548024.
^ Andrews, Bill (22 December 2019). "Scientists Find the Universe's First Molecule". Discover. Retrieved 22 December 2019.

[chebi33688-1] "hydridohelium(1+) (CHEBI:33688)". Chemical Entities of Biological Interest (ChEBI). European Bioinformatics Institute.

[2] "Helium hydride". American Chemical Society.

[EngelEtAl-3] Cite error: The named reference EngelEtAl was invoked but never defined (see the help page).

[chebi33689-4] "Hydridohelium (CHEBI:33689)". Chemical Entities of Biological Interest (ChEBI). European Bioinformatics Institute.

[stut2019-5] Güsten, Rolf; Wiesemeyer, Helmut; Neufeld, David; Menten, Karl M.; Graf, Urs U.; Jacobs, Karl; Klein, Bernd; Ricken, Oliver; Risacher, Christophe; Stutzki, Jürgen (April 2019). "Astrophysical detection of the helium hydride ion HeH⁺". Nature. 568 (7752): 357–359. arXiv:1904.09581. Bibcode:2019Natur.568..357G. doi:10.1038/s41586-019-1090-x. PMID 30996316. S2CID 119548024.

[DSCVR-20191222-6] Andrews, Bill (22 December 2019). "Scientists Find the Universe's First Molecule". Discover. Retrieved 22 December 2019.

[1]

[2]

[3]

[4]

[5]

[6]