| Hydrogen astatide | |
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| Identifiers | |
| PubChem | 23996 |
| ChemSpider | 22432 |
| ChEBI | CHEBI:30418 |
| Gmelin Reference | 532398 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | HAt |
| Molar mass | 211 g mol−1 |
| Exact mass | 211.008 g mol-1 |
| Related compounds | |
| Related compounds | Bismuthine Caesium hydride |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Hydrogen astatide, also known as astatane, or astidohydrogen is a chemical compound with the chemical formula HAt, consisting of an astatine atom covalently bonded to a hydrogen atom.[1]
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 since it will readily decompose into elemental hydrogen and astatine,[2] 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,[3] dissociation could easily result in the hydrogen carrying the negative charge. Thus, a hydrogen astatide sample can undergo the following reaction:
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,[4] as the astatine will decay into other elements.