# Polonide > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Polonide > Markdown URL: https://mediated.wiki/source/Polonide.md > Source: https://en.wikipedia.org/wiki/Polonide > Source revision: 1346264588 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Short description|Chemical compound containing polonium}} [[File:Magnesium-polonide-xtal-1960-3D-SF.png|thumb|right|A space-filling representation of the crystal structure of [magnesium polonide](/source/magnesium_polonide): Mg2+ ions are shown in green, while Po2− ions are shown in brown.]] thumb|Polonide A '''polonide''' is a [chemical compound](/source/chemical_compound) of the [radioactive](/source/radioactive) element [polonium](/source/polonium) with any [element](/source/Chemical_element) less [electronegative](/source/Electronegativity) than polonium.{{RedBook2005|pages=69, 260}}. Polonides are usually prepared by a direct reaction between the elements at temperatures of around 300–400 °C.{{citation | last = Moyer | first = Harvey V. | contribution = Chemical Properties of Polonium | pages = 33–96 | title = Polonium | url = http://www.osti.gov/bridge/servlets/purl/4367751-nEJIbm/ | editor-last = Moyer | editor-first = Harvey V. | id = TID-5221 | doi = 10.2172/4367751 |osti=4367751 | year = 1956 | location = Oak Ridge, Tenn. | publisher = United States Atomic Energy Commission| doi-access = free }}.{{citation | first = K. W. | last = Bagnall | title = The Chemistry of Polonium | journal = Adv. Inorg. Chem. Radiochem. | year = 1962 | volume = 4 | pages = 197–229 | url = https://books.google.com/books?id=8qePsa3V8GQC&pg=PA197 | isbn = 978-0-12-023604-6 | doi=10.1016/S0065-2792(08)60268-X| series = Advances in Inorganic Chemistry and Radiochemistry | url-access = subscription }}. They are amongst the most chemically stable compounds of polonium,{{Greenwood&Earnshaw1st|page=899}}. 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. Some polonides are intermediate between these two cases and others are [non-stoichiometric](/source/non-stoichiometric) compounds. [Alloy](/source/Alloy)s containing polonium are also classed as polonides. As polonium is immediately below [tellurium](/source/tellurium) in the periodic table, there are many [chemical and structural similarities](/source/periodic_table) between polonides and [telluride](/source/Telluride_(chemistry))s. ==Naturally occurring polonides== [Lead polonide](/source/Lead_polonide) (PbPo) occurs naturally, as [lead](/source/lead) is produced in the [alpha decay](/source/alpha_decay) of polonium.{{cite journal |last1=Weigel |first1=F. |year=1959 |title=Chemie des Poloniums |journal=[Angewandte Chemie](/source/Angewandte_Chemie) |volume=71 |issue=9 |pages=289–316 |doi=10.1002/ange.19590710902|bibcode=1959AngCh..71..289W }} ==Ionic polonides== The polonides of the most [electropositive](/source/Electronegativity) metals show classic ionic structural types, and can be considered to contain the Po2− anion. {| class="wikitable" |- ! Formula ! Structure ! Lattice
parameter ! Ref. |- | [Na2Po](/source/sodium_polonide) | [anti-fluorite](/source/anti-fluorite_structure) | 747.3(4) pm | |- | [CaPo](/source/calcium_polonide) | [halite (NaCl)](/source/sodium_chloride) | 651.0(4) pm | |- | [BaPo](/source/barium_polonide) | [halite (NaCl)](/source/sodium_chloride) | 711.9 pm | |- |} With smaller cations, the structural types suggest greater polarization of the polonide ion, or greater [covalency](/source/covalent_bond) in the bonding. [Magnesium polonide](/source/Magnesium_polonide) is unusual as it is not isostructural with magnesium telluride: MgTe has a [wurtzite structure](/source/wurtzite_structure),{{citation | first = W. | last = Zachariasen | journal = Z. Phys. Chem. | year = 1927 | volume = 128 | pages = 417–20 |title=Über die Kristallstruktur des Magnesiumtellurids |doi=10.1515/zpch-1927-12830| s2cid = 99161358 }}. although a [nickeline](/source/nickeline)-type phase has also been reported.{{citation | journal = J. Phys. Chem. Solids | volume = 67 | issue = 8 | year = 2006 | pages = 1668–73 | doi = 10.1016/j.jpcs.2006.02.017 | title = High pressure study of structural and electronic properties of magnesium telluride | first1 = D. | last1 = Rached | first2 = M. | last2 = Rabah | first3 = R. | last3 = Khenata | first4 = N. | last4 = Benkhettou | first5 = H. | last5 = Baltache | first6 = M. | last6 = Maachou | first7 = M. | last7 = Ameri|bibcode = 2006JPCS...67.1668R }}. {| class="wikitable" |- ! Formula ! Structure ! Lattice
parameter ! Ref. |- | [MgPo](/source/Magnesium_polonide) | [nickeline (NiAs)](/source/Nickeline) | ''a'' = 434.5 pm
''c'' = 707.7 pm | |- | [BePo](/source/beryllium_polonide) | [sphalerite (ZnS)](/source/Sphalerite) | 582.7 pm | |- | [CdPo](/source/cadmium_polonide) | [sphalerite (ZnS)](/source/Sphalerite) | 666.5 pm | |- | [ZnPo](/source/zinc_polonide) | [sphalerite (ZnS)](/source/Sphalerite) | 628(2) pm | |- |} The [effective radius](/source/Ionic_radius) of the polonide ion (Po2−) can be calculated from the Shannon (1976) ionic radii of the cations:{{citation | first= R. D. | last = Shannon | title = Revised Effective Ionic Radii and Systematic Studies of Interatomic Distances in Halides and Chalcogenides | journal = Acta Crystallogr. A| year = 1976 | volume = 32 | pages = 751–67 | doi = 10.1107/S0567739476001551|bibcode = 1976AcCrA..32..751S | issue= 5 | doi-access = }}. 216 pm for 4-coordination, 223 pm for 6-coordination, 225 pm for 8-coordination. The effect of the [lanthanide contraction](/source/lanthanide_contraction) is clear, in that the 6-coordinate telluride ion (Te2−) has an ionic radius of 221 pm. The lanthanides also form sesquipolonides of formula Ln2Po3, which can be considered to be ionic compounds.{{citation | url = https://www.osti.gov/opennet/servlets/purl/16137309-oYiakP/16137309.pdf | title = Heat Sources for Thermoelectric Generators | publisher = Monsanto Research Corporation Mound Laboratory | location = Miamisburg, Ohio | year = 1963}}. ==Intermetallic polonides== The [lanthanide](/source/lanthanide)s form very stable polonides of formula LnPo with the [halite (NaCl) structure](/source/Halite). Many of them seem to involve trivalent lanthanides (though Sm, Eu, and Yb with more stable +2 oxidation states are exceptions), making them resemble [electride](/source/electride)s. They are isostructural to the lanthanide sulfides, selenides, and tellurides.{{citation | journal = J. Inorg. Nucl. Chem. | volume = 28 | issue = 8 | year = 1966 | pages = 1581–88 | doi = 10.1016/0022-1902(66)80054-4 | title = Rare earth polonides | first1 = C. J. | last1 = Kershner | first2 = R. J. | last2 = DeSando | first3 = R. F. | last3 = Heidelberg | first4 = R. H. | last4 = Steinmeyer}}. {{citation | journal = J. Inorg. Nucl. Chem. | volume = 32 | issue = 9 | year = 1970 | pages = 2911–18 | doi = 10.1016/0022-1902(70)80355-4 | title = Promethium polonide synthesis and characterization | first1 = C. J. | last1 = Kershner | first2 = R. J. | last2 = Desando}}. These compounds are stable to at least 1600 °C (the melting point of thulium polonide, TmPo, is 2200 °C), in contrast to the ionic polonides (including the lanthanide sesquipolonides Ln2Po3), which decompose at around 600 °C. The thermal stability and non-volatility of these compounds (polonium metal boils at 962 °C) is important for their use in polonium-based heat sources. Mercury and lead also form 1:1 polonides. Platinum forms a compound formulated as PtPo2, while nickel forms a continuous series of phases NiPo''x'' (''x'' = 1–2). Gold also forms solid solutions with polonium over a wide range of compositions,{{citation | title = The Preparation and Identification of some Intermetallic Compounds of Polonium | first1 = W. G. | last1 = Witteman | first2 = A. L. | last2 = Giorgi | first3 = D. T. | last3 = Vier | journal = J. Phys. Chem. | year = 1960 | volume = 64 | issue = 4 | pages = 434–40 | doi = 10.1021/j100833a014}}. while bismuth and polonium are completely miscible. No reaction is observed between polonium and aluminium, carbon, iron, molybdenum, tantalum or tungsten. == See also == *[Polonium hydride](/source/Polonium_hydride), also known as hydrogen polonide ==References== {{reflist}} {{Polonium compounds}} {{Monatomic anion compounds}} * Category:Polonides Category:Anions --- Adapted from the Wikipedia article [Polonide](https://en.wikipedia.org/wiki/Polonide) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Polonide?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.