Editing Polonium (section)

==Characteristics==
<sup>210</sup>Po is an [[alpha decay|alpha emitter]] that has a half-life of 138.4&nbsp;days; it decays directly to its stable [[decay product|daughter isotope]], [[lead|<sup>206</sup>Pb]]. A milligram (5&nbsp;[[Curie (unit)|curie]]s) of <sup>210</sup>Po emits about as many alpha particles per second as 5&nbsp;grams of [[radium|<sup>226</sup>Ra]],<ref name="anl" /> which means it is 5,000 times more radioactive than radium. A few [[Curie (unit)|curie]]s (1&nbsp;curie equals 37&nbsp;[[Becquerel|gigabecquerels]], 1&nbsp;Ci = 37&nbsp;GBq) of <sup>210</sup>Po emit a blue glow which is caused by [[Ionized-air glow|ionisation]] of the surrounding air.

About one in 100,000&nbsp;alpha emissions causes an excitation in the nucleus which then results in the emission of a [[gamma ray]] with a maximum energy of 803&nbsp;keV.<ref>[[#Greenwood|Greenwood]], p. 250</ref><ref>{{cite web|url=http://atom.kaeri.re.kr/cgi-bin/decay?Po-210%20A|title=210PO α decay|work=Nuclear Data Center, Korea Atomic Energy Research Institute|date= 2000|access-date=2009-05-05}}</ref>

===Solid state form===
[[File:alpha po lattice.jpg|thumb|left|The alpha form of solid polonium]]
Polonium is a radioactive element that exists in two [[metal]]lic [[allotrope]]s. The alpha form is the only known example of a [[cubic (crystal system)|simple cubic]] crystal structure in a single atom basis at [[Standard temperature and pressure|STP]] ([[space group]] Pm{{overline|3}}m, no. 221). The unit cell has an edge length of 335.2 [[picometer]]s; the beta form is [[rhombohedral]].<ref>[[#Greenwood|Greenwood]], p. 753</ref><ref>{{cite book |first1=Gary L. |last1=Miessler |first2=Donald A. |last2=Tarr |title=Inorganic Chemistry |edition=3rd |page=[https://archive.org/details/inorganicchemist03edmies/page/285 285] |isbn=978-0-13-120198-9 |date=2004 |publisher=Pearson Prentice Hall |location=Upper Saddle River, N.J. |url=https://archive.org/details/inorganicchemist03edmies/page/285 }}</ref><ref>{{cite web| url = http://cst-www.nrl.navy.mil/lattice/struk/a_i.html| archive-url = https://web.archive.org/web/20010204004200/http://cst-www.nrl.navy.mil/lattice/struk/a_i.html| archive-date = 2001-02-04|date= 2000-11-20|work=Naval Research Laboratory |title = The beta Po (A_i) Structure| access-date = 2009-05-05}}</ref> The structure of polonium has been characterized by [[X-ray]] [[diffraction]]<ref>{{cite journal |last=Desando |first=R. J. |author2=Lange, R. C. |date=1966 |title=The structures of polonium and its compounds—I α and β polonium metal |journal=Journal of Inorganic and Nuclear Chemistry |volume=28 |issue=9 |pages=1837–1846 |doi=10.1016/0022-1902(66)80270-1}}</ref><ref>{{cite journal |last=Beamer |first=W. H. |author2=Maxwell, C. R. |date=1946 |title=The Crystal Structure of Polonium |journal=Journal of Chemical Physics |volume=14 |issue=9 |page=569 |doi=10.1063/1.1724201|hdl=2027/mdp.39015086430371 |hdl-access=free }}</ref> and [[electron diffraction]].<ref>{{cite journal |last1=Rollier |first1=M. A. |last2=Hendricks |first2=S. B.|last3= Maxwell|first3=L. R. |date=1936 |title=The Crystal Structure of Polonium by Electron Diffraction |journal=Journal of Chemical Physics |volume=4 |issue=10 |page=648 |doi=10.1063/1.1749762 |bibcode = 1936JChPh...4..648R|doi-access=free }}</ref>

<sup>210</sup>Po has the ability [[Volatility (chemistry)|to become airborne with ease]]: if a sample is heated in air to {{convert|55|C|F}}, 50% of it is vaporized in 45 hours to form [[diatomic molecule|diatomic]] Po<sub>2</sub> molecules, even though the melting point of polonium is {{convert|254|C|F}} and its boiling point is {{convert|962|C|F}}.<ref>{{cite journal| first1 = Bogdan |last1=Wąs| first2 = Ryszard |last2=Misiak| first3 = Mirosław |last3=Bartyzel| first4 = Barbara |last4=Petelenz | title = Thermochromatographic separation of <sup>206,208</sup>Po from a bismuth target bombarded with protons | journal =Nukleonika | date =2006| volume =51 | issue = Suppl. 2 | pages = s3–s5 | url =http://www.ichtj.waw.pl/ichtj/nukleon/back/full/vol51_2006/v51s2p03f.pdf}}</ref><ref name="CRC">{{RubberBible86th}}</ref><ref name="Thayer p78" />
More than one hypothesis exists for how polonium does this; one suggestion is that small clusters of polonium atoms are [[spallation|spalled off]] by the alpha decay.<ref>{{cite conference|title=Pseudo-evaporation of high specific activity alpha-emitting materials|author1= Condit, Ralph H.|author2=Gray, Leonard W.| author3=Mitchell, Mark A.|url=https://www.osti.gov/biblio/1162255| conference=EFCOG 2014 Safety Analysis Workshop|year=2014|publisher=Lawrence Livermore National Laboratory|osti= 1162255|conference-url=https://www.osti.gov/biblio/1169821}}</ref>

===Chemistry===
The chemistry of polonium is similar to that of [[tellurium]], although it also shows some similarities to its neighbor [[bismuth]] due to its metallic character. Polonium dissolves readily in dilute [[acid]]s but is only slightly [[solubility|soluble]] in [[alkali]]s. Polonium [[Solution (chemistry)|solution]]s are first colored in pink by the Po<sup>2+</sup> ions, but then rapidly become yellow because alpha radiation from polonium ionizes the solvent and converts Po<sup>2+</sup> into Po<sup>4+</sup>. As polonium also emits alpha-particles after disintegration, this process is accompanied by bubbling and emission of heat and light by [[Laboratory glassware|glassware]] due to the absorbed alpha particles; as a result, polonium solutions are volatile and will evaporate within days unless sealed.<ref name="nbb" /><ref>[[#Bagnall|Bagnall]], p. 206</ref> At pH about 1, polonium ions are readily hydrolyzed and complexed by acids such as [[oxalic acid]], [[citric acid]], and [[tartaric acid]].<ref>{{Ullmann | first1=Cornelius |last1=Keller |first2=Walter |last2=Wolf |first3=Jashovam |last3=Shani | title = Radionuclides, 2. Radioactive Elements and Artificial Radionuclides | doi = 10.1002/14356007.o22_o15}}</ref>

====Compounds====
Polonium has no common compounds, and almost all of its compounds are synthetically created; more than 50 of those are known.<ref>[[#Bagnall|Bagnall]], p. 199</ref> The most stable class of polonium compounds are [[polonide]]s, which are prepared by direct reaction of two elements. [[sodium polonide|Na<sub>2</sub>Po]] has the [[antifluorite]] structure, the polonides of [[calcium polonide|Ca]], [[barium polonide|Ba]], [[mercury polonide|Hg]], Pb and lanthanides form a NaCl lattice, [[beryllium polonide|BePo]] and [[cadmium polonide|CdPo]] have the [[wurtzite]] and [[magnesium polonide|MgPo]] the [[nickel arsenide]] structure. Most polonides decompose upon heating to about 600&nbsp;°C, except for HgPo that decomposes at ~300&nbsp;°C and the [[lanthanide]] polonides, which do not decompose but melt at temperatures above 1000&nbsp;°C. For example, the polonide of [[praseodymium]] (PrPo) melts at 1250&nbsp;°C, and that of [[thulium]] (TmPo) melts at 2200&nbsp;°C.<ref name="g766">[[#Greenwood|Greenwood]], p. 766</ref> [[lead polonide|PbPo]] is one of the very few naturally occurring polonium compounds, as polonium [[alpha decay]]s to form [[lead]].<ref>{{cite journal |last1=Weigel |first1=F. |date=1959 |title=Chemie des Poloniums |journal=[[Angewandte Chemie]] |volume=71 |pages=289–316 |doi=10.1002/ange.19590710902 |issue=9|bibcode=1959AngCh..71..289W }}</ref>

[[Polonium hydride]] ({{chem|Po||H|2}}) is a volatile liquid at room temperature prone to dissociation; it is thermally unstable.<ref name="g766" /> [[properties of water|Water]] is the only other known [[hydrogen chalcogenide]] which is a liquid at room temperature; however, this is due to hydrogen bonding. The three oxides, [[polonium monoxide|PoO]], [[polonium dioxide|PoO<sub>2</sub>]] and [[polonium trioxide|PoO<sub>3</sub>]], are the products of oxidation of polonium.<ref>{{cite book| author = Holleman, A. F.| author2 = Wiberg, E. |title = Inorganic Chemistry| publisher = Academic Press| location = San Diego| date = 2001| isbn = 978-0-12-352651-9}}</ref>

[[Halide]]s of the structure PoX<sub>2</sub>, PoX<sub>4</sub> and PoF<sub>6</sub> are known. They are soluble in the corresponding hydrogen halides, i.e., PoCl<sub>X</sub> in HCl, PoBr<sub>X</sub> in HBr and PoI<sub>4</sub> in HI.<ref name="figgins" /> Polonium dihalides are formed by direct reaction of the elements or by reduction of PoCl<sub>4</sub> with SO<sub>2</sub> and with PoBr<sub>4</sub> with H<sub>2</sub>S at room temperature. Tetrahalides can be obtained by reacting polonium dioxide with HCl, HBr or HI.<ref name="g765">[[#Greenwood|Greenwood]], pp. 765, 771, 775</ref>

Other polonium compounds include the [[polonite]], [[potassium polonite]]; various [[polonate]] solutions; and the [[acetate]], [[bromate]], [[carbonate]], [[citrate]], [[Chromate ion|chromate]], cyanide, [[formate]], [[polonium(II) hydroxide|(II)]] or [[polonium(IV) hydroxide|(IV)]] hydroxide, [[polonium tetranitrate|nitrate]], [[polonium selenate|selenate]], [[polonium selenite|selenite]], monosulfide, [[sulfate]], [[polonium disulfate|disulfate]] or [[polonium sulfite|sulfite]] salts.<ref name="figgins">Figgins, P. E. (1961) [http://www.osti.gov/bridge/purl.cover.jsp?purl=/4034029-SolPsF/ The Radiochemistry of Polonium], National Academy of Sciences, US Atomic Energy Commission, pp. 13–14 [https://books.google.com/books?id=N0MrAAAAYAAJ Google Books]</ref><ref>[[#Bagnall|Bagnall]], pp. 212–226</ref>

A limited [[organopolonium chemistry]] is known, mostly restricted to dialkyl and diaryl polonides (R<sub>2</sub>Po), triarylpolonium halides (Ar<sub>3</sub>PoX), and diarylpolonium dihalides (Ar<sub>2</sub>PoX<sub>2</sub>).<ref name="Z">{{cite book |last=Zingaro |first=Ralph A. |chapter=Polonium: Organometallic Chemistry |date=2011 |title=Encyclopedia of Inorganic and Bioinorganic Chemistry |publisher=John Wiley & Sons |pages=1–3 |doi=10.1002/9781119951438.eibc0182|isbn=9781119951438 }}</ref><ref name="M">{{cite journal |last1=Murin |first1=A. N. |last2=Nefedov |first2=V. D. |first3=V. M. |last3=Zaitsev |first4=S. A. |last4=Grachev |date=1960 |title=Production of organopolonium compounds by using chemical alterations taking place during the β-decay of RaE |url=http://www.mathnet.ru/links/d4bd811f2ded6e2b1d67f43a93e2910e/dan23789.pdf |journal=Dokl. Akad. Nauk SSSR |volume=133 |issue=1 |pages=123–125 |access-date=12 April 2020 |language=ru}}</ref> Polonium also forms soluble compounds with some [[ligand]]s, such as [[2,3-butanediol]] and [[thiourea]].<ref name="Z" />

{|class="wikitable" style="text-align:center"
|+Polonium compounds<ref name="g765" /><ref>Wiberg, Egon; Holleman, A. F. and Wiberg, Nils [https://books.google.com/books?id=Mtth5g59dEIC&pg=PA594 Inorganic Chemistry], Academic Press, 2001, p. 594, {{ISBN|0-12-352651-5}}.</ref>
|-
!Formula!!Color!! [[melting point|m.p.]] (°C)|| [[Sublimation (phase transition)|Sublimation]] <br/>temp. (°C) ||Symmetry||[[Pearson symbol]] || [[Space group]] ||No||a (pm) || b(pm) || c(pm) || Z || [[density|ρ]] (g/cm<sup>3</sup>) ||ref
|-
|[[polonium monoxide|PoO]]|| black|| || || || || || || || || || || ||
|-
|[[polonium dioxide|PoO<sub>2</sub>]]|| pale yellow|| 500 (dec.) ||885 ||[[face-centered cubic|fcc]] ||cF12||Fm{{overline|3}}m ||225 ||563.7||563.7||563.7||4|| 8.94 || <ref name="Bagnall">{{cite journal |last1=Bagnall |first1=K. W. |last2=d'Eye |first2=R. W. M. |date=1954 |title=The Preparation of Polonium Metal and Polonium Dioxide |journal=[[Journal of the Chemical Society|J. Chem. Soc.]] |pages=4295–4299|doi=10.1039/JR9540004295 }}</ref>
|-
|[[polonium hydride|PoH<sub>2</sub>]]|| || -35.5 || || || || || || || || || || ||
|-
|[[polonium dichloride|PoCl<sub>2</sub>]]|| dark ruby red|| 355 ||130 ||[[orthorhombic]] ||oP3||Pmmm||47 ||367||435||450||1|| 6.47 || <ref name="PoCl">{{cite journal|doi=10.1039/JR9550002320|title=The polonium halides. Part I. Polonium chlorides|date=1955|last1=Bagnall|first1=K. W.|last2=d'Eye|first2=R. W. M.|last3=Freeman|first3=J. H.|journal=Journal of the Chemical Society (Resumed)|pages=2320–2326 }}</ref>
|-
|[[polonium dibromide|PoBr<sub>2</sub>]]||purple-brown|| 270 (dec.)|| || || || || || || || || || ||<ref name="PoBr">{{cite journal|doi=10.1039/JR9550003959|title=The polonium halides. Part II. Bromides|date=1955|last1=Bagnall|first1=K. W.|last2=d'Eye|first2=R. W. M.|last3=Freeman|first3=J. H.|journal=Journal of the Chemical Society (Resumed)|pages=3959–3963 }}</ref>
|-
|[[polonium tetrachloride|PoCl<sub>4</sub>]]|| yellow||300 || 200 ||[[monoclinic]] || || || || || || || || ||<ref name="PoCl" />
|-
|[[polonium tetrabromide|PoBr<sub>4</sub>]]|| red||330 (dec.) || ||[[face-centered cubic|fcc]] || cF100 || Fm{{overline|3}}m ||225||560||560||560||4|| || <ref name="PoBr" />
|-
|[[polonium tetraiodide|PoI<sub>4</sub>]]||black || || || || || || || || || || || || <ref>{{cite journal|doi=10.1039/JR9560003385|title=657. The polonium halides. Part III. Polonium tetraiodide|date=1956|last1=Bagnall|first1=K. W.|last2=d'Eye|first2=R. W. M.|last3=Freeman|first3=J. H.|journal=Journal of the Chemical Society (Resumed)|pages=3385–3389 }}</ref>
|}
{{col-begin}}
{{col-break}}
'''Oxides'''
* [[Polonium monoxide|PoO]]
* [[Polonium dioxide|PoO<sub>2</sub>]]
* [[Polonium trioxide|PoO<sub>3</sub>]]
{{col-break}}
'''Hydrides'''
* [[Polonium hydride|PoH<sub>2</sub>]]
{{col-break}}
'''[[Halide]]s'''
* PoX<sub>2</sub> (except PoF<sub>2</sub>)
* PoX<sub>4</sub>
* [[Polonium hexafluoride|PoF<sub>6</sub>]]
* PoBr<sub>2</sub>Cl<sub>2</sub> (salmon pink)
{{col-end}}

===Isotopes===
{{Main|Isotopes of polonium}}
Polonium has 42 known isotopes, all of which are [[radioactivity|radioactive]]. They have [[atomic mass]]es that range from 186 to 227 [[atomic mass unit|u]]. [[polonium-210|<sup>210</sup>Po]] (half-life 138.376&nbsp;days) is the most widely available and is manufactured via neutron capture by natural [[bismuth]]. It also naturally occurs as a trace in uranium ores, as it is the penultimate member of the decay chain of <sup>238</sup>U. The longer-lived <sup>209</sup>Po (half-life 124 years, longest-lived of all polonium isotopes){{NUBASE2020|ref}} and <sup>208</sup>Po (half-life 2.9&nbsp;years) can be manufactured through the alpha, proton, or deuteron bombardment of [[lead]] or bismuth in a [[cyclotron]].<ref name="emsley">{{cite book|last=Emsley|first=John|title=Nature's Building Blocks: An A-Z Guide to the Elements|edition=New|date=2011|publisher=Oxford University Press|location=New York, NY|isbn=978-0-19-960563-7|page=415}}</ref>