Difference between revisions of "Polonide"
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! Structure | ! Structure | ||
! Lattice<br/>parameter | ! Lattice<br/>parameter | ||
| − | ! | + | ! Ref. |
|- | |- | ||
| Na<sub>2</sub>Po | | Na<sub>2</sub>Po | ||
| − | | anti-fluorite | + | | [[Fluorite structure|anti-fluorite]] |
| 747.3(4) pm | | 747.3(4) pm | ||
| <ref name="G&E"/><ref name="AEC-chem"/> | | <ref name="G&E"/><ref name="AEC-chem"/> | ||
|- | |- | ||
| CaPo | | CaPo | ||
| − | | halite | + | | [[Halite structure|halite (NaCl)]] |
| 651.0(4) pm | | 651.0(4) pm | ||
| <ref name="G&E"/><ref name="AEC-chem"/> | | <ref name="G&E"/><ref name="AEC-chem"/> | ||
|- | |- | ||
| BaPo | | BaPo | ||
| − | | halite | + | | [[Halite structure|halite (NaCl)]] |
| | | | ||
| <ref name="G&E"/> | | <ref name="G&E"/> | ||
|- | |- | ||
|} | |} | ||
| + | |||
| + | With smaller cations, the structural types suggest greater polarization of the polonide ion, or greater covalancy in the bonding. | ||
| + | |||
| + | {| class="wikitable" | ||
| + | |- | ||
| + | ! Formula | ||
| + | ! Structure | ||
| + | ! Lattice<br/>parameter | ||
| + | ! Ref. | ||
| + | |- | ||
| + | | MgPo | ||
| + | | [[Nickeline structure|nickeline (NiAs)]] | ||
| + | | | ||
| + | | <ref name="G&E"/> | ||
| + | |- | ||
| + | | BePo | ||
| + | | [[Sphalerite structure|sphalerite (ZnS)]] | ||
| + | | 582.7 pm | ||
| + | | <ref name="G&E"/><ref name="AEC-chem"/> | ||
| + | |- | ||
| + | | CdPo | ||
| + | | [[Sphalerite structure|sphalerite (ZnS)]] | ||
| + | | | ||
| + | | <ref name="G&E"/> | ||
| + | |- | ||
| + | | ZnPo | ||
| + | | [[Sphalerite structure|sphalerite (ZnS)]] | ||
| + | | 628(2) pm | ||
| + | | <ref name="AEC-chem"/> | ||
| + | |- | ||
| + | |} | ||
| + | |||
| + | ==Intermetallic polonides== | ||
| + | The [[lanthanoid]]s form very stable polonides of formula LnPo with the [[Halite structure|halite (NaCl) structure]]: as the +2 oxidation state is disfavoured for most lanthanoids, these are probably best described as intermetallic compounds rather than charge-separated ionic species.<ref name="G&E"/> | ||
| + | |||
| + | Mercury and lead also form 1:1 polonides.<ref name="G&E"/><ref name="AEC-chem"/> | ||
==References== | ==References== | ||
Revision as of 06:59, 26 May 2010
A polonide is a chemical compound of polonium with an element from groups 1–15 of the periodic table (including hydrogen, the lanthanoids and the actinoids).[1] Polonides are amongst the most stable compounds of polonium,[2] and can be divided into two broad groups:
- ionic polonides, which appear to contain the Po2− anion;
- intermetallic polonides, in which the bonding is more complex.
As well as polonides which are intermediate between these two cases, there are also non-stoichiometric polonides and alloys of polonium. As would be expected from periodicity, polonides are often structurally and chemically similar to tellurides. Polonides are usually prepared by a direct reaction between the elements.[3]
Ionic polonides
The polonides of the most electropositive metals show classic ionic structural types, and can be considered to contain the Po2− anion.
| Formula | Structure | Lattice parameter |
Ref. |
|---|---|---|---|
| Na2Po | anti-fluorite | 747.3(4) pm | [2][3] |
| CaPo | halite (NaCl) | 651.0(4) pm | [2][3] |
| BaPo | halite (NaCl) | [2] |
With smaller cations, the structural types suggest greater polarization of the polonide ion, or greater covalancy in the bonding.
| Formula | Structure | Lattice parameter |
Ref. |
|---|---|---|---|
| MgPo | nickeline (NiAs) | [2] | |
| BePo | sphalerite (ZnS) | 582.7 pm | [2][3] |
| CdPo | sphalerite (ZnS) | [2] | |
| ZnPo | sphalerite (ZnS) | 628(2) pm | [3] |
Intermetallic polonides
The lanthanoids form very stable polonides of formula LnPo with the halite (NaCl) structure: as the +2 oxidation state is disfavoured for most lanthanoids, these are probably best described as intermetallic compounds rather than charge-separated ionic species.[2]
Mercury and lead also form 1:1 polonides.[2][3]
References
- ↑ Nomenclature of Inorganic Chemistry; IUPAC Recommendations 2005; Royal Society of Chemistry: Cambridge, 2005; pp 69,260. ISBN 0-85404-438-8, <http://www.iupac.org/publications/books/rbook/Red_Book_2005.pdf>.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; p 899. ISBN 0-08-022057-6.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Moyer, Harvey V. Chemical Properties of Polonium. In Polonium; Moyer, Harvey V., Ed.; United States Atomic Energy Commission: Oak Ridge, Tenn., 1956; pp 33–96. TID-5221. doi:10.2172/4367751, <http://www.osti.gov/bridge/servlets/purl/4367751-nEJIbm/>.
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