 | |||
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| Names | |||
|---|---|---|---|
| IUPAC name Hydrogen astatide[1] | |||
| Systematic IUPAC name Astatane[2] | |||
| Identifiers | |||
3D model (JSmol) | |||
| ChEBI | |||
| ChemSpider |
| ||
| 532398 | |||
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| Properties | |||
| HAt | |||
| Molar mass | 211 g·mol−1 | ||
| Boiling point | −3 °C (27 °F; 270 K) estimated[3] | ||
| Soluble | |||
| Conjugate acid | Astatonium | ||
| Conjugate base | Astatide | ||
| Related compounds | |||
Otheranions | Hydrogen fluoride | ||
Othercations | Sodium astatide | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Hydrogen astatide, also known asastatine hydride,astatane,astatidohydrogen orhydroastatic acid, is a chemical compound with thechemical formula HAt, consisting of anastatineatomcovalently bonded to ahydrogen atom.[4] It thus is ahydrogen halide.
Thischemical compound can dissolve in water to form hydroastatic acid, which exhibits properties very similar to the other fivebinary acids, and is in fact the strongest among them. However, it is limited in use due to its ready decomposition into elemental hydrogen and astatine,[5] as well as the short half-life of the variousisotopes of astatine. Because the atoms have a nearly equalelectronegativity, and as theAt+ ion has been observed,[6] dissociation could easily result in thehydrogen carrying the negative charge. Thus, a hydrogen astatide sample can undergo the following reaction:
This results in elemental hydrogengas and astatineprecipitate. Furthermore, a trend for hydrogen halides, or HX, is thatenthalpy of formation becomes less negative, i.e., decreases in magnitude but increases in absolute terms, as the halide becomes larger. Whereas 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 stableisotopes. The most stable is astatine-210, which has ahalf-life of approximately 8.1 hours, making itschemical compounds especially difficult to work with,[7] as the astatine will quicklydecay into other elements.
Hydrogen astatide can be produced by reacting astatine with hydrocarbons (such asethane):[8]
This reaction also produces the corresponding alkyl astatide, in this case ethyl astatide (astatoethane).
