Hydrogen astatide

Hydrogen astatide
Identifiers
PubChem	23996
ChemSpider	22432 Y
ChEBI	CHEBI:30418 Y
Gmelin Reference	532398
Jmol-3D images	Image 1
SMILES [AtH]
InChI InChI=1S/AtH/h1H Y Key: PGLQOBBPBPTBQS-UHFFFAOYSA-N Y InChI=1/AtH/h1H Key: PGLQOBBPBPTBQS-UHFFFAOYAG
Properties
Molecular formula	HAt
Molar mass	211.00 g mol−1
Related compounds
Other anions	Hydrogen bromide Hydrogen chloride Hydrogen fluoride Hydrogen iodide
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Hydrogen astatide, also known as astatine hydride, astatane, or astidohydrogen, is a chemical compound with the chemical formula HAt, consisting of an astatine atom covalently bonded to a hydrogen atom.

This chemical compound exhibits properties very similar to the other four hydrogen halides, and is in fact the strongest acid among them; however, it is limited in use due to its ready decomposition into elemental hydrogen and astatine, as well as the short half-life of the various isotopes of astatine. Because the atoms have a nearly equal electronegativity, and as the At⁺ ion has been observed, dissociation could easily result in the hydrogen carrying the negative charge. Thus, a hydrogen astatide sample can undergo the following reaction:

2 HAt → H⁺ + At⁻ + H⁻ + At⁺ → H₂ + At₂

This results in elemental hydrogen gas and astatine precipitate. Further, a trend for hydrogen halides, or HX, is that enthalpy of formation lowers as the period increases for the halide. While hydroiodic acid solutions are stable, the hydronium-astatide solution is clearly less stable than the water-hydrogen-astatine system. Finally, radiolysis from astatine nuclei could sever the H-At bonds.

Additionally, astatine has no stable isotopes; of which the most stable is astatine-210, which has a half-life of approximately 8.1 hours, making its chemical compounds especially difficult to work with, as the astatine will quickly decay into other elements.