 | |
 Polonium, Po Hydrogen, H | |
| Names | |
|---|---|
| Preferred IUPAC name Polonium hydride | |
| Systematic IUPAC name Polane | |
Other names
| |
| Identifiers | |
3D model (JSmol) | |
| ChEBI | |
| ChemSpider | |
| 25163, 169602 | |
| |
| Properties | |
| PoH2 | |
| Molar mass | 210.998 g/mol |
| Melting point | −35.3 °C (−31.5 °F; 237.8 K)[1] |
| Boiling point | 36.1 °C (97.0 °F; 309.2 K)[1] |
| Conjugate base | Polonide |
| Structure | |
| Bent | |
| Related compounds | |
Otheranions | H2O H2S H2Se H2Te |
Othercations | TlH3 PbH4 BiH3 HAt |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Polonium hydride (also known aspolonium dihydride,hydrogen polonide, orpolane) is a chemical compound with the formulaPoH2. It is aliquid at room temperature, the secondhydrogen chalcogenide with this property afterwater. It is very unstable chemically and tends to decompose into elementalpolonium andhydrogen. It is avolatile and verylabile compound, from which manypolonides can be derived. Additionally, it is radioactive.[2]
Polonium hydride cannot be produced by direct reaction from the elements upon heating. Other unsuccessful routes to synthesis include the reaction ofpolonium tetrachloride (PoCl4) withlithium aluminium hydride (LiAlH4), which only produces elemental polonium, and the reaction ofhydrochloric acid withmagnesium polonide (MgPo). The fact that these synthesis routes do not work may be caused by theradiolysis of polonium hydride upon formation.[3]
Trace quantities of polonium hydride may be prepared by reacting hydrochloric acid with polonium-platedmagnesium foil. In addition, thediffusion of trace quantities of polonium inpalladium orplatinum that is saturated with hydrogen (seepalladium hydride) may be due to the formation and migration of polonium hydride.[3]
Polonium hydride is a more covalent compound than most metal hydrides because polonium straddles the border betweenmetals andmetalloids and has some nonmetallic properties. It is intermediate between ahydrogen halide likehydrogen chloride and ametal hydride likestannane.
It should have properties similar to that ofhydrogen selenide andhydrogen telluride, otherborderline hydrides. It is expected to be anendothermic compound, like the lighter hydrogen telluride and hydrogen selenide, and therefore would decompose into its constituent elements, releasing heat in the process. The amount of heat given off in the decomposition of polonium hydride is over 100kJ/mol, the largest of all the hydrogenchalcogenides.
It is predicted that, like the other hydrogen chalcogenides, polonium may form two types ofsalts:polonide (containing the Po2−anion) and one from polonium hydride (containing –PoH, which would be the polonium analogue ofthiol,selenol andtellurol). However, no salts from polonium hydride are known. An example of a polonide islead polonide (PbPo), which occurs naturally aslead is formed in thealpha decay of polonium.[4]
Polonium hydride is difficult to work with due to the extremeradioactivity of polonium and its compounds and has only been prepared in very dilute tracer quantities. As a result, its physical properties are not definitely known.[3] It is also unknown if polonium hydride forms anacidic solution in water like its lighter homologues, or if it behaves more like a metal hydride (see alsohydrogen astatide).
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