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{{distinguish|Plutonium}} | |||
{{Sprotected}} | |||
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{{Elementbox_header | number=84 | symbol=Po | name=polonium | left=] | right=] | above=] | below=] | color1=#cccc99 | color2=black }} | |||
{{Use dmy dates|date=September 2022}} | |||
{{Elementbox_series | ]s }} | |||
{{infobox polonium}} | |||
{{Elementbox_groupperiodblock | group=16 | period=6 | block=p }} | |||
'''Polonium''' is a ]; it has ] '''Po''' and ] 84. A rare and highly ] ] (although sometimes classified as a ]) with no stable ], polonium is a ] and chemically similar to ] and ], though its metallic character resembles that of its ] in the ]: ], ], and ]. Due to the short ] of all its isotopes, its natural occurrence is limited to tiny traces of the fleeting ] (with a half-life of 138 days) in ] ]s, as it is the ] of natural ]. Though longer-lived isotopes exist, such as the 124 years half-life of polonium-209, they are much more difficult to produce. Today, polonium is usually produced in milligram quantities by the ] of ]. Due to its intense radioactivity, which results in the ] of chemical bonds and radioactive self-heating, its chemistry has mostly been investigated on the trace scale only. | |||
{{Elementbox_appearance | silvery }} | |||
{{Elementbox_atomicmass_gpm | ] }} | |||
{{Elementbox_econfig | []] 4f<sup>14</sup> 5d<sup>10</sup> 6s<sup>2</sup> 6p<sup>4</sup> }} | |||
{{Elementbox_epershell | 2, 8, 18, 32, 18, 6 }} | |||
{{Elementbox_section_physicalprop | color1=#cccc99 | color2=black }} | |||
{{Elementbox_phase | ] }} | |||
{{Elementbox_density_gpcm3nrt | (alpha) 9.196 }} | |||
{{Elementbox_density_gpcm3nrt | (beta) 9.398 }} | |||
{{Elementbox_meltingpoint | k=527 | c=254 | f=489 }} | |||
{{Elementbox_boilingpoint | k=1235 | c=962 | f=1764 }} | |||
{{Elementbox_heatfusion_kjpmol | ca. 13 }} | |||
{{Elementbox_heatvaporiz_kjpmol | 102.91 }} | |||
{{Elementbox_heatcapacity_jpmolkat25 | 26.4 }} | |||
{{Elementbox_vaporpressure_katpa | | | | (846) | 1003 | 1236 | comment= }} | |||
{{Elementbox_section_atomicprop | color1=#cccc99 | color2=black }} | |||
{{Elementbox_crystalstruct | cubic }} | |||
{{Elementbox_oxistates | '''4''', 2<br />(] oxide) }} | |||
{{Elementbox_electroneg_pauling | 2.0 }} | |||
{{Elementbox_ionizationenergies1 | 812.1 }} | |||
{{Elementbox_atomicradius_pm | ] }} | |||
{{Elementbox_atomicradiuscalc_pm | ] }} | |||
{{Elementbox_section_miscellaneous | color1=#cccc99 | color2=black }} | |||
{{Elementbox_magnetic | nonmagnetic }} | |||
{{Elementbox_eresist_ohmmat0 | (α) 0.40 µ}} | |||
{{Elementbox_thermalcond_wpmkat300k | ? 20 }} | |||
{{Elementbox_thermalexpansion_umpmkat25 | 23.5 }} | |||
{{Elementbox_cas_number | 7440-08-6 }} | |||
{{Elementbox_isotopes_begin | color1=#cccc99 | color2=black }} | |||
{{Elementbox_isotopes_decay2 | mn=208 | sym=Po | |||
| na=] | hl=2.898 ] | |||
| dm1=] | de1=5.215 | pn1=204 | ps1=] | |||
| dm2=], ] | de2=1.401 | pn2=208 | ps2=] }} | |||
{{Elementbox_isotopes_decay2 | mn=209 | sym=Po | |||
| na=] | hl=103 y | |||
| dm1=] | de1=4.979 | pn1=205 | ps1=] | |||
| dm2=], ] | de2=1.893 | pn2=209 | ps2=] }} | |||
{{Elementbox_isotopes_decay | mn=210 | sym=Po | |||
| na=] | hl=138.376 ] | |||
| dm=] | de=5.407 | pn=206 | ps=] }} | |||
{{Elementbox_isotopes_end}} | |||
{{Elementbox_footer | color1=#cccc99 | color2=black }} | |||
Polonium was discovered on July 18, 1898 by ] and ], when it was extracted from the uranium ore ]<ref>{{Cite web |title=Polonium (Po) {{!}} AMERICAN ELEMENTS ® |url=https://www.americanelements.com/po.html |access-date=2024-04-17 |website=American Elements: The Materials Science Company |language=en}}</ref> and identified solely by its strong radioactivity: it was the first element to be discovered in this way.<ref>{{cite journal | last1=Radvanyi | first1=Pierre | last2=Villain | first2=Jacques | title=The discovery of radioactivity | journal=Comptes Rendus. Physique | volume=18 | issue=9–10 | date=November 1, 2017 | pages=544–550 | doi=10.1016/j.crhy.2017.10.008 | bibcode=2017CRPhy..18..544R | url = https://www.sciencedirect.com/science/article/pii/S1631070517300786}}</ref> Polonium was named after Marie Skłodowska-Curie's homeland of Poland, which at the time was ] between three countries. Polonium has few applications, and those are related to its radioactivity: heaters in ]s, ]s, sources of ]s and ]s, and ] (e.g., ]). It is extremely dangerous to humans. | |||
'''Polonium''' (]: {{IPA|/pə(ʊ)ˈləʊniəm/}}) is a ] in the ] that has the symbol '''Po''' and ] 84. A rare ] ], polonium is chemically similar to ] and ] and occurs in ] ores. Polonium has been studied for possible use in heating ]. It exists as ]. | |||
== |
==Characteristics== | ||
When it is mixed or ]ed with ], polonium can be a ] source: beryllium releases a neutron upon absorption of an alpha particle that is supplied by <sup>210</sup>Po. It has been used in this capacity as a ] for ]s. Other uses include: | |||
* Devices that eliminate static charges in ] mills and other places. However, ] sources are more commonly used and are less dangerous. Another alternative is to use a high voltage direct current power supply to ionize air positively or negatively. | |||
* Brushes that remove accumulated dust from ]s. The polonium used in these brushes is sealed and controlled thus minimizing radiation hazards. | |||
* As <sup>210</sup>Po, a lightweight heat source to power ]. | |||
* Radioactive poison . | |||
<sup>210</sup>Po is an ] that has a half-life of 138.4 days; it decays directly to its stable ], ]. A milligram (5 ]s) of <sup>210</sup>Po emits about as many alpha particles per second as 5 grams of ],<ref name="anl" /> which means it is 5,000 times more radioactive than radium. A few ]s (1 curie equals 37 ], 1 Ci = 37 GBq) of <sup>210</sup>Po emit a blue glow which is caused by ] of the surrounding air. | |||
== History == | |||
Also called "Radium F", polonium was discovered by ] and her husband ] in ]<ref>{{cite journal|author = Curie P., Curie M.|title =. |journal = Comptes Rendus|year = 1898|volume=126|pages=1101}}</ref> and was later named after Marie's native land of ] (]: ''Polonia'').<ref>{{cite journal | |||
About one in 100,000 alpha emissions causes an excitation in the nucleus which then results in the emission of a ] with a maximum energy of 803 keV.<ref>], 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> | |||
| title = Borders of the Nuclear World --- 100 Years After Discovery of Polonium | |||
| author = Pfützner M. | |||
===Solid state form=== | |||
] | |||
Polonium is a radioactive element that exists in two ]lic ]s. The alpha form is the only known example of a ] crystal structure in a single atom basis at ] (] Pm{{overline|3}}m, no. 221). The unit cell has an edge length of 335.2 ]s; the beta form is ].<ref>], p. 753</ref><ref>{{cite book |first1=Gary L. |last1=Miessler |first2=Donald A. |last2=Tarr |title=Inorganic Chemistry |edition=3rd |page= |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 ] ]<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 ].<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 ]: if a sample is heated in air to {{convert|55|C|F}}, 50% of it is vaporized in 45 hours to form ] 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 ] 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 ], although it also shows some similarities to its neighbor ] due to its metallic character. Polonium dissolves readily in dilute ]s but is only slightly ] in ]s. Polonium ]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 so this process is accompanied by bubbling and emission of heat and light by ] due to the absorbed alpha particles; as a result, polonium solutions are volatile and will evaporate within days unless sealed.<ref name="nbb" /><ref>], p. 206</ref> At pH about 1, polonium ions are readily hydrolyzed and complexed by acids such as ], ], and ].<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>], p. 199</ref> The most stable class of polonium compounds are ]s, which are prepared by direct reaction of two elements. ] has the ] structure, the polonides of ], ], ], Pb and lanthanides form a NaCl lattice, ] and ] have the ] and ] the ] structure. Most polonides decompose upon heating to about 600 °C, except for HgPo that decomposes at ~300 °C and the ] polonides, which do not decompose but melt at temperatures above 1000 °C. For example, the polonide of ] (PrPo) melts at 1250 °C, and that of ] (TmPo) melts at 2200 °C.<ref name="g766">], p. 766</ref> ] is one of the very few naturally occurring polonium compounds, as polonium ]s to form ].<ref>{{cite journal |last1=Weigel |first1=F. |date=1959 |title=Chemie des Poloniums |journal=] |volume=71 |pages=289–316 |doi=10.1002/ange.19590710902 |issue=9|bibcode=1959AngCh..71..289W }}</ref> | |||
] ({{chem|Po||H|2}}) is a volatile liquid at room temperature prone to dissociation; it is thermally unstable.<ref name="g766" /> ] is the only other known ] which is a liquid at room temperature; however, this is due to hydrogen bonding. The three oxides, ], ] and ], 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> | |||
]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">], pp. 765, 771, 775</ref> | |||
Other polonium compounds include the ], ]; various ] solutions; and the ], ], ], ], ], cyanide, ], ] or ] hydroxide, ], ], ], monosulfide, ], ] or ] salts.<ref name="figgins">Figgins, P. E. (1961) , National Academy of Sciences, US Atomic Energy Commission, pp. 13–14 </ref><ref>], pp. 212–226</ref> | |||
A limited ] 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 ]s, such as ] and ].<ref name="Z" /> | |||
{|class="wikitable" style="text-align:center" | |||
|+Polonium compounds<ref name="g765" /><ref>Wiberg, Egon; Holleman, A. F. and Wiberg, Nils , Academic Press, 2001, p. 594, {{ISBN|0-12-352651-5}}.</ref> | |||
|- | |||
!Formula!!Color!! ] (°C)|| ] <br/>temp. (°C) ||Symmetry||] || ] ||No||a (pm) || b(pm) || c(pm) || Z || ] (g/cm<sup>3</sup>) ||ref | |||
|- | |||
|]|| black|| || || || || || || || || || || || | |||
|- | |||
|]|| pale yellow|| 500 (dec.) ||885 ||] ||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=] |pages=4295–4299|doi=10.1039/JR9540004295 }}</ref> | |||
|- | |||
|]|| || -35.5 || || || || || || || || || || || | |||
|- | |||
|]|| dark ruby red|| 355 ||130 ||] ||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> | |||
|- | |||
|]||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> | |||
|- | |||
|]|| yellow||300 || 200 ||] || || || || || || || || ||<ref name="PoCl" /> | |||
|- | |||
|]|| red||330 (dec.) || ||] || cF100 || Fm{{overline|3}}m ||225||560||560||560||4|| || <ref name="PoBr" /> | |||
|- | |||
|]||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''' | |||
* ] | |||
* ] | |||
* ] | |||
{{col-break}} | |||
'''Hydrides''' | |||
* ] | |||
{{col-break}} | |||
''']s''' | |||
* PoX<sub>2</sub> (except PoF<sub>2</sub>) | |||
* PoX<sub>4</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 ]. They have ]es that range from 186 to 227 ]. ] (half-life 138.376 days) is the most widely available and is manufactured via neutron capture by natural ]. 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 years) can be manufactured through the alpha, proton, or deuteron bombardment of ] or bismuth in a ].<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> | |||
==History== | |||
Tentatively called "]", polonium was discovered by ] and Pierre Curie in July 1898,<ref name="c1">{{cite journal|author1=Curie, P. |author2=Curie, M. |title=Sur une substance nouvelle radio-active, contenue dans la pechblende |trans-title=On a new radioactive substance contained in pitchblende |language=fr |journal=Comptes Rendus |volume=127 |pages=175–178 |date=1898 |url=http://www.academie-sciences.fr/activite/archive/dossiers/Curie/Curie_pdf/CR1898_p175_178.pdf |url-status=unfit |archive-url=https://web.archive.org/web/20130723022419/http://www.academie-sciences.fr/activite/archive/dossiers/Curie/Curie_pdf/CR1898_p175_178.pdf |archive-date=July 23, 2013 }} </ref><ref>{{Cite web|url=http://elements.vanderkrogt.net/element.php?sym=po|title=84. Polonium – Elementymology & Elements Multidict|last=Krogt|first=Peter van der|website=elements.vanderkrogt.net|access-date=2017-04-26}}</ref> and was named after Marie Curie's native land of ] ({{langx|la|Polonia}}).<ref>{{cite journal | |||
| title = Borders of the Nuclear World – 100 Years After Discovery of Polonium | |||
| last = Pfützner | first =M. | |||
| journal = Acta Physica Polonica B | | journal = Acta Physica Polonica B | ||
| volume = 30 | | volume = 30 | ||
| issue 5 | | issue = 5 | date = 1999 | ||
| |
| page= 1197 | ||
| bibcode =1999AcPPB..30.1197P}}</ref><ref>{{cite journal | |||
| pages = 1197 | |||
| url =http://adsabs.harvard.edu/abs/1999AcPPB..30.1197P}}</ref> | |||
<ref>{{cite journal | |||
| title = The centennial of the 1903 Nobel Prize for physics | | title = The centennial of the 1903 Nobel Prize for physics | ||
| |
| last = Adloff | first = J. P. | ||
| journal = |
| journal = Radiochimica Acta | ||
| volume = 91 | | volume = 91 | ||
| issue |
| issue = 12–2003 | ||
| pages=681–688 | |||
| year = 681-688 | |||
| |
| date=2003 | ||
| doi = 10.1524/ract.91.12.681.23428| s2cid = 120150862 }}</ref> Poland at the time was under ], ], and ] ], and did not exist as an independent country. It was Curie's hope that naming the element after her native land would publicize its lack of independence. Polonium may be the first element named to highlight a political controversy.<ref name="Przemysl">{{cite journal | |||
| doi = 10.1524/ract.91.12.681.23428}}</ref> | |||
Poland at the time was under Russian, Prussian and Austrian ], and not recognized as an independent country. It was Marie's hope that naming the element after her native land would add notoriety to its plight. Polonium may be the first element named to highlight a political controversy.<ref>{{cite journal | |||
| title = Chemical and Polish aspects of polonium and radium discovery | | title = Chemical and Polish aspects of polonium and radium discovery | ||
| |
| last = Kabzinska | first =K. | ||
| journal = |
| journal = Przemysł Chemiczny | ||
| volume = 77 | | volume = 77 | ||
| |
| date = 1998 | ||
| |
| pages = 104–107 | ||
| |
| issue = 3}}</ref> | ||
This element was the first one discovered by the Curies while they were investigating the cause of ] ]. Pitchblende, after removal of the radioactive elements ] and ], was more radioactive than the uranium and thorium combined. This spurred the Curies to search for additional radioactive elements. They first separated out polonium from pitchblende in July 1898, and five months later, also isolated ].<ref name="nbb" /><ref name="c1" /><ref name="c2">{{cite journal |author1=Curie, P. |author2=Curie, M. |author3=Bémont, G. |title=Sur une nouvelle substance fortement radio-active contenue dans la pechblende |trans-title=On a new, strongly radioactive substance contained in pitchblende |language=fr |journal=Comptes Rendus |volume=127 |pages=1215–1217 |date=1898 |url=http://www.academie-sciences.fr/activite/archive/dossiers/Curie/Curie_pdf/CR1898_p1215_1217.pdf |archive-url=https://web.archive.org/web/20130722232602/http://www.academie-sciences.fr/activite/archive/dossiers/Curie/Curie_pdf/CR1898_p1215_1217.pdf |archive-date=July 22, 2013 }} {{Webarchive|url=https://web.archive.org/web/20090806083923/http://www.aip.org/history/curie/discover.htm |date=6 August 2009 }}</ref> German scientist ] successfully isolated 3 milligrams of polonium in 1902, though at the time he believed it was a new element, which he dubbed "radio-tellurium", and it was not until 1905 that it was demonstrated to be the same as polonium.<ref>{{cite journal | title = Polonium and Radio-Tellurium | journal = Nature | volume = 73 | issue = 549 | pages = 549 |date = 1906 | doi = 10.1038/073549b0| bibcode = 1906Natur..73R.549. | doi-access = free }}</ref><ref>{{cite book |last = Neufeldt |first = Sieghard | title = Chronologie Chemie: Entdecker und Entdeckungen | publisher = John Wiley & Sons | year = 2012 | isbn = 9783527662845 | url = {{Google books|0lFQjLAlgC0C|plainurl=y|page=115}} }}</ref> | |||
This element was the first one discovered by the Curies while they were investigating the cause of ] ]. The pitchblende, after removal of uranium and radium, was more radioactive than both radium and uranium put together. This spurred them on to find the element. The electroscope showed it separating with ]. | |||
In the United States, polonium was produced as part of the ]'s ] during ]. Polonium and ] were the key ingredients of the ']' initiator at the center of the bomb's spherical ].<ref name="nwfaq41">. Nuclearweaponarchive.org. Retrieved on 2013-04-28.</ref> 'Urchin' initiated the ] at the moment of ]ity to ensure that the weapon did not ]. 'Urchin' was used in early U.S. weapons; subsequent U.S. weapons utilized a pulse neutron generator for the same purpose.<ref name="nwfaq41" /> | |||
== Occurrence == | |||
A very rare element in nature, polonium is found in ] ores at about 100 ]s per ] (1:10<sup>10</sup>). Its natural abundance is approximately 0.2% of the abundance of radium. Polonium has been found in ] from tobacco leaves grown with phosphate fertilizers.<ref>{{cite journal| author = Kilthau, Gustave F.|title = Cancer risk in relation to radioactivity in tobacco |journal = Radiologic Technology | volume = 67| issue = | pages = 217-222 |pim =8850254}}</ref><ref></ref> | |||
Much of the basic physics of polonium was ] until after the war. The fact that a polonium-beryllium (Po-Be) initiator was used in the gun-type nuclear weapons was classified until the 1960s.<ref name="FAS_Project">{{cite web | author=US Department of Energy Office of Declassification | title=Restricted data declassification decisions, 1946 to the present (RDD-7) | website=FAS Project on Government Secrecy (1991-2021), fas.org | date=2001-01-01 | url=https://sgp.fas.org/othergov/doe/rdd-7.html#I16 | access-date=2024-01-30}}</ref> | |||
=== Synthesis by (n,g) reaction === | |||
The ] and the ] funded ] using polonium on five people at the ] between 1943 and 1947. The people were administered between {{convert|9|and|22|μCi|kBq|lk=on}} of polonium to study its ].<ref name="congress1986"> {{Webarchive|url=https://web.archive.org/web/20130730200210/http://contentdm.library.unr.edu/cdm4/item_viewer.php?CISOROOT=%2Fconghear&CISOPTR=102&CISOBOX=1&REC=1#metajump |date=2013-07-30 }}. United States. Congress. House. of the Committee on Energy and Commerce. Subcommittee on Energy Conservation and Power, published by U.S. Government Printing Office, 1986, Identifier Y 4.En 2/3:99-NN, Electronic Publication Date 2010, at the University of Nevada, Reno, unr.edu</ref><ref name="nes1950">"Studies of polonium metabolism in human subjects", Chapter 3 in ''Biological Studies with Polonium, Radium, and Plutonium'', National, Nuclear Energy Series, Volume VI-3, McGraw-Hill, New York, 1950, cited in "American Nuclear Guinea Pigs ...", 1986 House Energy and Commerce committee report</ref><ref>Moss, William and Eckhardt, Roger (1995) , Los Alamos Science, Number 23.</ref> | |||
In ] an experiment showed that when natural ] is bombarded with ]s, <sup>210</sup>Bi, which is the parent of polonium, was created. Polonium may now be made in milligram amounts in this procedure which uses high neutron fluxes found in ]s. Only about 100 grams is produced each year, making polonium exceedingly rare.<ref>http://www.rsc.org/chemistryworld/News/2006/November/27110601.asp RSC Chemistry World Q&A</ref> | |||
==Occurrence and production== | |||
=== Synthesis by (p,n) and (p,2n) reactions === | |||
Polonium is a very rare element in nature because of the short ] of all its isotopes. Nine isotopes, from 210 to 218 inclusive, occur in ] as ]: <sup>210</sup>Po, <sup>214</sup>Po, and <sup>218</sup>Po occur in the ] of ]; <sup>211</sup>Po and <sup>215</sup>Po occur in the decay chain of ]; <sup>212</sup>Po and <sup>216</sup>Po occur in the decay chain of ]; and <sup>213</sup>Po and <sup>217</sup>Po occur in the decay chain of ]. (No primordial <sup>237</sup>Np survives, but traces of it are continuously regenerated through (n,2n) knockout reactions in natural <sup>238</sup>U.)<ref name=4n1>{{cite journal |last1=Peppard |first1=D. F. |last2=Mason |first2=G. W. |last3=Gray |first3=P. R. |last4=Mech |first4=J. F. |title=Occurrence of the (4n + 1) series in nature |journal=Journal of the American Chemical Society |date=1952 |volume=74 |issue=23 |pages=6081–6084 |doi=10.1021/ja01143a074 |bibcode=1952JAChS..74.6081P |url=https://digital.library.unt.edu/ark:/67531/metadc172698/m2/1/high_res_d/metadc172698.pdf }}</ref> Of these, <sup>210</sup>Po is the only isotope with a half-life longer than 3 minutes.<ref name="po484">{{Cite journal| last1=Carvalho|first1=F.|last2=Fernandes|first2=S.|last3=Fesenko|first3=S. |last4=Holm|first4=E.|last5=Howard|first5=B.|last6=Martin|first6=P.|last7=Phaneuf|first7=P. |last8=Porcelli|first8=D.|last9=Pröhl|first9=G.|last10=Twining|first10=J.|title=The Environmental Behaviour of Polonium|journal=Technical Reports Series – International Atomic Energy Agency|series=Technical reports series|volume=484|publisher=International Atomic Energy Agency|location=Vienna|date=2017|page=1|isbn=978-92-0-112116-5}}</ref> | |||
Polonium can be found in ] ores at about 0.1 mg per ] (1 part in 10<sup>10</sup>),<ref>], p. 746</ref><ref>], p. 198</ref> which is approximately 0.2% of the abundance of radium. The amounts in the Earth's crust are not harmful. Polonium has been found in ] from tobacco leaves grown with ] fertilizers.<ref>{{cite journal| last = Kilthau | first = Gustave F. |title = Cancer risk in relation to radioactivity in tobacco |journal = Radiologic Technology |volume = 67 |pages = 217–222| pmid = 8850254| date = 1996| issue = 3}}</ref><ref>{{cite web|url=http://kidslink.bo.cnr.it/besta/fumo/epolonio.html |title=Alpha Radioactivity (210 Polonium) and Tobacco Smoke |access-date=2009-05-05 |url-status=dead |archive-url=https://web.archive.org/web/20130609055245/http://kidslink.bo.cnr.it/besta/fumo/epolonio.html |archive-date=June 9, 2013 }}</ref><ref name="Muggli08">{{cite journal |title = Waking a Sleeping Giant: The Tobacco Industry's Response to the Polonium-210 Issue |last1 = Monique | first1 = E. Muggli |journal = American Journal of Public Health |volume = 98 |issue = 9| date = 2008 |pmid = 18633078|pmc = 2509609 |doi = 10.2105/AJPH.2007.130963 |pages = 1643–50 |last2 = Ebbert |first2 = Jon O. |last3 = Robertson |first3 = Channing |last4 = Hurt |first4 = Richard D.}}</ref> | |||
It has been found that by ] bombardment of bismuth using a ] that the longer lived isotopes of polonium can be formed. Other more proton rich isotopes can be formed by the irradation of platinium with ] nuclei.<ref>{{cite journal| author = Atterling, H., Forsling, W.|title = Light Polonium Isotopes from Carbon Ion Bombardments of Platinum |journal = Arkiv for Fysik | volume = 15| issue = 1 | pages = 81-88 |year = 1959|url =http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=4238755}}</ref> | |||
Because it is present in small concentrations, isolation of polonium from natural sources is a tedious process. The largest batch of the element ever extracted, performed in the first half of the 20th century, contained only {{convert|40|Ci|TBq|abbr=on}} (9 mg) of ] and was obtained by processing 37 tonnes of residues from radium production.<ref>{{cite journal|author=Adloff, J. P.|author2=MacCordick, H. J.|name-list-style=amp|title=The Dawn of Radiochemistry|journal=Radiochimica Acta|volume=70/71|pages=13–22|date=1995|issue=Supplement |url=http://www.nucleonica.com/Articles/Article03/Article3.htm|doi=10.1524/ract.1995.7071.special-issue.13|s2cid=99790464}}, reprinted in {{cite book|url = https://books.google.com/books?id=whGiCQywLi8C&pg=PA17|title = One hundred years after the discovery of radioactivity|isbn = 978-3-486-64252-0|last1 = Adloff|first1 = J. P.|date = 1996|page = 17|publisher = Walter de Gruyter GmbH}}{{Dead link|date=May 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Polonium is now usually obtained by irradiating bismuth with high-energy neutrons or protons.<ref name="nbb" /><ref name="g249">], p. 249</ref> | |||
== Isotopes == | |||
Polonium has ], all of which are ]. They have ]es that range from 194 u to 218 u. <sup>210</sup>Po is the most widely available. <sup>209</sup>Po (] 103 years) and <sup>208</sup>Po (half-life 2.9 years) can be made through the alpha, proton, or deuteron bombardment of ] or ] in a ]. However these isotopes are expensive to produce. | |||
In 1934, an experiment showed that when natural ] is bombarded with ]s, <sup>210</sup>Bi is created, which then decays to <sup>210</sup>Po via beta-minus decay. By irradiating certain bismuth salts containing light element nuclei such as beryllium, a cascading (α,n) reaction can also be induced to produce <sup>210</sup>Po in large quantities.<ref>{{cite journal |title =Neutronic Chain Reactions for Polonium-210 Production |first =Solomon |last = Lim |journal = SSRN |date = 2023 |doi = 10.2139/ssrn.4469519|s2cid =264176122 |url =https://hal.science/hal-04196973/file/Report%20210.pdf }}</ref> The final purification is done pyrochemically followed by liquid-liquid extraction techniques.<ref>{{cite journal |title =Pyrochemical Extraction of Polonium from Irradiated Bismuth Metal |first =Wallace W. |last = Schulz |author2 = Schiefelbein, Gary F. |author3 = Bruns, Lester E. |journal = Ind. Eng. Chem. Process Des. Dev. |date = 1969 |volume = 8 |issue = 4 |pages= 508–515| doi = 10.1021/i260032a013}}</ref> Polonium may now be made in milligram amounts in this procedure which uses high neutron fluxes found in ]s.<ref name="g249" /> Only about 100 grams are produced each year, practically all of it in Russia, making polonium exceedingly rare.<ref>{{cite web |title = Q&A: Polonium-210 |url =http://www.rsc.org/chemistryworld/News/2006/November/27110601.asp |publisher = RSC Chemistry World |date = 2006-11-27 |access-date =2009-01-12}}</ref><ref>{{cite web |date=2007-01-11 |title=Most Polonium Made Near the Volga River |url=https://www.themoscowtimes.com/archive/most-polonium-made-near-the-volga-river |publisher=The Moscow Times – News}}</ref> | |||
All elements containing 84 or more protons are radioactive. Alpha decay is a common form of decay for these nuclei. The most stable isotopes with more than 84 protons are ] and ]; which form an "]" which renders them stable enough to be found in large quantities in nature, but heavier nuclei are more and more affected by ]. | |||
This process can cause problems in ] based ] such as those used in the ]'s ]. Measures must be taken in these reactors to deal with the unwanted possibility of <sup>210</sup>Po being released from the coolant.<ref>{{cite journal|title=Long-lived radionuclides of sodium, lead-bismuth, and lead coolants in fast-neutron reactors|journal=Atomic Energy|volume =87|issue=3 |year=1999|pages=658–662|doi=10.1007/BF02673579|last1=Usanov|first1=V. I.|last2=Pankratov|first2=D. V.|last3=Popov|first3=É. P.|last4=Markelov|first4=P. I.|last5=Ryabaya|first5=L. D.|last6=Zabrodskaya|first6=S. V.|s2cid=94738113}}</ref><ref>{{cite journal|author=Naumov, V. V. |date=November 2006|url=http://www.antiatom.ru/2006_12-11.php|script-title=ru:За какими корабельными реакторами будущее?|language=ru|journal= Атомная стратегия |volume= 26}}</ref> | |||
=== <sup>210</sup>Po === | |||
Polonium-210 is an ] that has a half-life of 138.376 days. A milligram of <sup>210</sup>Po emits as many alpha particles as 5 grams of ]. A great deal of energy is released by its decay with half a gram quickly reaching a temperature above 750 K. A few ]s (1 curie equals 37 ]) of <sup>210</sup>Po emit a blue glow which is caused by ] of surrounding air. A single gram of <sup>210</sup>Po generates 140 watts of power.<ref>, Argonne National Laboratory</ref> Because it emits many ], which are stopped within a very short distance in dense media and release their energy, <sup>210</sup>Po has been used as a lightweight heat source to power ] in ]s. A <sup>210</sup>Po heat source was also used in each of the ] rovers deployed on the surface of the ], to keep their internal components warm during the lunar nights. Some anti-static brushes contain up to 500 microcuries of <sup>210</sup>Po as a source of charged particles for neutralizing static electricity in materials like photographic film.<ref>http://www.amstat.com/solutions/staticmaster.html</ref> The majority of the time <sup>210</sup>Po decays only by emission of an ], not by emission of an alpha particle and a ]. About one in a 100000 decays results in the emission of a gamma ray, this low gamma ray production rate makes it more difficult to find and identify this isotope. Rather than gamma ray spectroscopy, alpha spectroscopy will be the best method of measuring this isotope. | |||
The longer-lived isotopes of polonium, <sup>208</sup>Po and <sup>209</sup>Po, can be formed by ] or ] bombardment of bismuth using a ]. Other more neutron-deficient and more unstable isotopes can be formed by the irradiation of platinum with ] nuclei.<ref>{{cite journal| author = Atterling, H.| author2 = Forsling, W. |title = Light Polonium Isotopes from Carbon Ion Bombardments of Platinum |journal = Arkiv för Fysik |volume = 15| issue = 1 |pages = 81–88 |date = 1959 |osti =4238755}}</ref> | |||
== Chemical characteristics == | |||
Polonium dissolves readily in dilute ]s, but is only slightly ] in ]s. It is closely related chemically to bismuth and tellurium. <sup>210</sup>Po (in common with ]) has the ability ]: if a sample is heated in air to 328 K (55°C, 131°F), 50% of it is vaporized in 45 hours, even though the melting point of polonium is 527 K (254°C, 489°F) and its boiling point is 1235 K (962°C, 1763°F).<ref>{{cite journal | |||
| author = Bogdan Wąs, Ryszard Misiak, Mirosław Bartyzel, Barbara Petelenz | |||
| title = Thermochromatographic Separation of <sup>206</sup>,<sup>208</sup>Po from a Bismuth Target Bombardet with Protons | |||
| journal =Nukleonica | |||
| year =2006 | |||
| volume =51 | |||
| issue = Suppl. 2 | |||
| pages = s3-s5 | |||
| url =http://www.ichtj.waw.pl/ichtj/nukleon/back/full/vol51_2006/v51s2p03f.pdf | |||
}}</ref> | |||
More than one hypothesis exists for how polonium does this; one suggestion is that small clusters of polonium atoms are ] by the alpha decay. | |||
==Applications== | |||
It has been reported that ] can ] polonium by the action of ].<ref> | |||
Polonium-based sources of alpha particles were produced in the former ].<ref name="rus1" /> Such sources were applied for measuring the thickness of industrial coatings via attenuation of alpha radiation.<ref>], p. 225</ref> | |||
{{cite journal | |||
| author = Momoshima N., Song L.X., Osaki S.,Maeda Y., | |||
| title = Formation and emission of volatile polonium compound by microbial activity and polonium methylation with methylcobalamin. | |||
| journal =Environ Sci Technol | |||
| year =2001 | |||
| volume =35 | |||
| issue = 15 | |||
| pages = 2956-2960 | |||
| url =http://www.medscape.com/medline/abstract/11478248?prt=true| | |||
| doi = 10.1021/es001730+ S0013-936X(00)01730-2}} | |||
</ref><ref> | |||
{{cite journal | |||
| author = Momoshima N., Song L.X., Osaki S.,Maeda Y., | |||
| title = Biologically induced Po emission from fresh water | |||
| journal =J Environ Radioact. | |||
| year = 2002 | |||
| volume = 63 | |||
| issue = 2 | |||
| pages = 187-197 | |||
| doi =10.1016/S0265-931X(02)00028-0}}</ref> | |||
Because of intense alpha radiation, a one-gram sample of <sup>210</sup>Po will spontaneously heat up to above {{convert|500|C|F}} generating about 140 watts of power. Therefore, <sup>210</sup>Po is used as an atomic heat source to power ]s via ] materials.<ref name="anl">{{cite web| url =http://www.ead.anl.gov/pub/doc/polonium.pdf | archive-url =https://web.archive.org/web/20070703021010/http://www.ead.anl.gov/pub/doc/polonium.pdf | archive-date =2007-07-03 |title = Polonium |publisher = Argonne National Laboratory| access-date = 2009-05-05}}</ref><ref name="nbb" /><ref name="g251">], p. 251</ref><ref>{{cite book |url=https://books.google.com/books?id=07TEK_w3A4AC&pg=PA183 |page=183 |last=Hanslmeier |first= Arnold |title= The sun and space weather |publisher=Springer |date=2002 |isbn=978-1-4020-0684-5}}</ref> For example, <sup>210</sup>Po heat sources were used in the ] 1 (1970) and Lunokhod 2 (1973) ] rovers to keep their internal components warm during the lunar nights, as well as the ] and 90 satellites (1965).<ref name="rus1">{{cite web |url=http://npc.sarov.ru/issues/sarovbook/section3p11.html |archive-url=https://web.archive.org/web/20070501055529/http://npc.sarov.ru/issues/sarovbook/section3p11.html |archive-date=May 1, 2007 |title=Радиоизотопные источники тепла |url-status=dead |access-date=June 1, 2016}} (in Russian). npc.sarov.ru</ref><ref>{{cite book | first = Andrew | last = Wilson | title = Solar System Log | location = London | publisher = Jane's Publishing Company Ltd | date = 1987 | page = | isbn = 978-0-7106-0444-6 | url = https://archive.org/details/solarsystemlog00andr/page/64 }}</ref> | |||
] | |||
== Solid state form == | |||
The alpha form of solid polonium is cubic with a distance of 3.352 Å between atoms. It is a simple ] solid which is not interpenetrated. | |||
The alpha particles emitted by polonium can be converted to neutrons using beryllium oxide, at a rate of 93 neutrons per million alpha particles.<ref name="g251" /> Po-BeO mixtures are used as passive ]s with a ]-to-] production ratio of 1.13 ± 0.05, lower than for ]-based neutron sources.<ref name="gtn">{{cite arXiv |last=Ritter |first=Sebastian |eprint=2111.02774 |title=Comparative Study of Gamma to Neutron Ratios of various (alpha, neutron) Neutron Sources |class=nucl-ex |date= 2021}}</ref> Examples of Po-BeO mixtures or ]s used as neutron sources are a ] for ]s<ref name="nbb">{{cite book| last = Emsley| first =John |title = Nature's Building Blocks| publisher = Oxford University Press| location = New York| date = 2001| pages = 330–332| isbn = 978-0-19-850341-5}}</ref><ref>{{cite book| author = Rhodes, Richard| title = Dark Sun: The Making of the Hydrogen Bomb| publisher = Walker & Company| location = New York| date = 2002| pages = | isbn = 978-0-684-80400-2| url = https://archive.org/details/darksunmakingofh00rhod/page/187}}</ref> and for inspections of oil wells. About 1500 sources of this type, with an individual activity of {{convert|1850|Ci|TBq|abbr=on}}, had been used annually in the Soviet Union.<ref> (in Russian). stringer.ru (2006-11-26).</ref> | |||
The beta form of polonium is ]; it has been reported in the chemical literature, along with the alpha form, several times. | |||
Polonium was also part of brushes or more complex tools that eliminate static charges in photographic plates, ] mills, paper rolls, sheet plastics, and on substrates (such as automotive) prior to the application of coatings.<ref name="BoiceCohen2014">{{cite journal |last1=Boice |first1=John D. |last2=Cohen |first2=Sarah S. |last3=Mumma |first3=Michael T. |last4=Ellis |first4=Elizabeth Dupree |last5=Cragle |first5=Donna L. |last6=Eckerman |first6=Keith F. |last7=Wallace |first7=Philip W. |last8=Chadda |first8=Bandana |last9=Sonderman |first9=Jennifer S. |last10=Wiggs |first10=Laurie D. |last11=Richter |first11=Bonnie S. |last12=Leggett |first12=Richard W. |title=Mortality Among Mound Workers Exposed to Polonium-210 and Other Sources of Radiation, 1944–1979 |journal=Radiation Research |volume=181 |issue=2 |date=2014 |pages=208–28 |doi=10.1667/RR13395.1 |pmid=24527690 |display-authors=2|bibcode=2014RadR..181..208B |osti=1286690 |s2cid=7350371 }}</ref> Alpha particles emitted by polonium ionize air molecules that neutralize charges on the nearby surfaces.<ref>{{cite web|url=http://www.thermo.com/eThermo/CMA/PDFs/Articles/articlesFile_16929.pdf |title=Static Control for Electronic Balance Systems |access-date=2009-05-05 |url-status=dead |archive-url=https://web.archive.org/web/20131110213624/http://www.thermo.com/eThermo/CMA/PDFs/Articles/articlesFile_16929.pdf |archive-date=November 10, 2013 }}</ref><ref>{{cite news| url =http://news.bbc.co.uk/1/hi/england/1868414.stm |title =BBC News : College breaches radioactive regulations| access-date = 2009-05-05|date=2002-03-12}}</ref> Some anti-static brushes contain up to {{convert|500|uCi|MBq|sigfig=1}} of <sup>210</sup>Po as a source of charged particles for neutralizing static electricity.<ref>{{cite web |url = http://www.amstat.com/solutions/staticmaster.html |title = Staticmaster Ionizing Brushes |publisher = AMSTAT Industries |access-date = 2009-05-05 |archive-date = 2009-09-26 |archive-url = https://web.archive.org/web/20090926032436/http://www.amstat.com/solutions/staticmaster.html |url-status = dead }}</ref> In the US, devices with no more than {{convert|500|μCi|MBq|abbr=on}} of (sealed) <sup>210</sup>Po per unit can be bought in any amount under a "general license",<ref>{{cite web| url = https://www.nrc.gov/reading-rm/doc-collections/cfr/part031/full-text.html| title = General domestic licenses for byproduct material| access-date = 2009-05-05}}</ref> which means that a buyer need not be registered by any authorities. Polonium needs to be replaced in these devices nearly every year because of its short half-life; it is also highly radioactive and therefore has been mostly replaced by less dangerous ] sources.<ref name="anl" /> | |||
Two papers report X-ray ] experiments on polonium metal.<ref>R.J. Desando and R.C Lange, ''Journal of Inorganic and Nuclear Chemistry'', 1966, '''28''', 1837-1846.</ref> | |||
<ref>W.H Beamer and C.R. Maxwell, ''Journal of Chemical Physics'', 1946, '''14''', 569-569.</ref> The first report of the crystal structure of polonium was done using ].<ref>M.A. Rollier, S.B. Hendricks and L.R. Maxwell, ''Journal of Chemical Physics'', 1936, '''4''', 648-652.</ref> | |||
Tiny amounts of <sup>210</sup>Po are sometimes used in the laboratory and for teaching purposes—typically of the order of {{convert|4|-|40|kBq|μCi|abbr=on}}, in the form of sealed sources, with the polonium deposited on a substrate or in a resin or polymer matrix—are often exempt from licensing by the NRC and similar authorities as they are not considered hazardous. Small amounts of <sup>210</sup>Po are manufactured for sale to the public in the United States as "needle sources" for laboratory experimentation, and they are retailed by scientific supply companies. The polonium is a layer of plating which in turn is plated with a material such as gold, which allows the ] (used in experiments such as cloud chambers) to pass while preventing the polonium from being released and presenting a toxic hazard.{{citation needed|date=February 2023}} | |||
== Tests == | |||
] | |||
===Gamma counting=== | |||
By means of radiometric methods such as ] (or a method using a chemical separation followed by an ] measurement with a non-energy-dispersive counter), it is possible to measure the concentrations of ] and to distinguish one from another. In practice, background noise would be present and depending on the detector, the line width would be larger which would make it harder to identify and measure the ]. In biological/medical work it is common to use the natural ] present in all tissues/body fluids as a check of the equipment and as an internal standard. | |||
Polonium ]s were marketed by ] from 1940 to 1953. While the amount of radiation from the plugs was minuscule and not a threat to the consumer, the benefits of such plugs quickly diminished after approximately a month because of polonium's short half-life and because buildup on the conductors would block the radiation that improved engine performance. (The premise behind the polonium spark plug, as well as ]'s prototype ] plug that preceded it, was that the radiation would improve ionization of the fuel in the cylinder and thus allow the motor to fire more quickly and efficiently.)<ref>{{cite web|url=https://www.orau.org/health-physics-museum/collection/consumer/miscellaneous/spark-plugs.html|title=Radioactive spark plugs|publisher=Oak Ridge Associated Universities|date=January 20, 1999|access-date=October 7, 2021}}</ref><ref>{{cite web|url=http://www.utoledo.edu/nsm/ic/elements/polonium.html|first=Cassandra|last=Pittman|title=Polonium|work=The Instrumentation Center|publisher=University of Toledo|date=February 3, 2017|access-date=August 23, 2018}}</ref> | |||
] | |||
===Alpha counting=== | |||
The best way to test for (and measure) many alpha emitters is to use ] is it is common to place a drop of the test solution on a metal disk which is then dried out to give a uniform coating on the disk. This is then used as the test sample. If the thickness of the layer formed on the disk is too thick then the lines of the spectrum are broadened, this is becuase some of the energy of the ]s is lost during their movement through the layer of active material. An alternative method is to use internal liquid sintillation where the sample is mixed with a sintillation cocktail. Then the light emitted is then counted, some machines will record the amount of light energy per radioactive decay event. Due to the imperfections of the liquid sintillation method (such as a failure for all the photons to be detected, cloudy or coloured samples can be difficult to count) and the fact that random quneching can reduce the number of photons generated per radioactive decay it is possible to get a broadening of the alpha spectra obtained through liquid sintillation. It is likely that these liquid sintillation spectra will be subject to a ] broadening rather than the distortion exhibited when the layer of a active material on a disk is too thick. | |||
==Biology and toxicity== | |||
A thrid energy dispersive method for counting alpha particles is to use a semiconductor detector. | |||
===Overview=== | |||
From left to right the peaks are due to <sup>209</sup>Po, <sup>210</sup>Po, <sup>239</sup>Pu and <sup>241</sup>Am. The fact that isotopes such as ] and ] have more than one alpha line indicates that the ] has the ability to be in different discrete ]s (like a molecule can). | |||
Polonium can be hazardous and has no biological role.<ref name="nbb" /> By mass, polonium-210 is around 250,000 times more toxic than ] (the {{LD50}} for <sup>210</sup>Po is less than 1 ] for an average adult (see below) compared with about 250 ] for hydrogen cyanide<ref>{{cite web| url = http://physchem.ox.ac.uk/MSDS/HY/hydrogen_cyanide.html | archive-url = https://archive.today/20020211054154/http://physchem.ox.ac.uk/MSDS/HY/hydrogen_cyanide.html | url-status = dead | archive-date = 2002-02-11 |title =Safety data for hydrogen cyanide|work= Physical & Theoretical Chemistry Lab, Oxford University}}</ref>). The main hazard is its intense radioactivity (as an alpha emitter), which makes it difficult to handle safely. Even in ] amounts, handling <sup>210</sup>Po is extremely dangerous, requiring specialized equipment (a negative pressure alpha ] equipped with high-performance filters), adequate monitoring, and strict handling procedures to avoid any contamination. Alpha particles emitted by polonium will damage organic tissue easily if polonium is ingested, inhaled, or absorbed, although they do not penetrate the ] and hence are not hazardous as long as the alpha particles remain outside the body and do not come near the eyes, which are living tissue. Wearing chemically resistant and intact gloves is a mandatory precaution to avoid transcutaneous ] of polonium directly through the ]. Polonium delivered in concentrated ] can easily diffuse through inadequate gloves (e.g., ]) or the acid may damage the gloves.<ref>], pp. 202–6</ref> | |||
Polonium does not have toxic chemical properties.<ref>{{Cite web|url=https://www.medicalnewstoday.com/articles/58088.php|title=Polonium-210: Effects, symptoms, and diagnosis|website=Medical News Today|date=28 July 2017}}</ref> | |||
== Toxicity == | |||
Polonium is a highly radioactive and toxic element and is very difficult to handle. | |||
Even in ] amounts, handling <sup>210</sup>Po is extremely dangerous, requiring specialized equipment and strict handling procedures. Alpha particles emitted by polonium will damage organic tissue easily if polonium is ingested, inhaled, or absorbed (though they do not penetrate the ] and hence are not hazardous if the polonium is outside the body). | |||
It has been reported that some ]s can ] polonium by the action of ].<ref>{{cite journal |last1= Momoshima | first1 =N.|last2= Song | first2 = L. X.|last3= Osaki | first3 =S.|last4=Maeda | first4 =Y.| title = Formation and emission of volatile polonium compound by microbial activity and polonium methylation with methylcobalamin | journal =Environ Sci Technol | date =2001 | volume =35 | issue = 15 | pages = 2956–2960 | doi = 10.1021/es001730| pmid =11478248| bibcode =2001EnST...35.2956M}}</ref><ref> | |||
The committed effective dose equivalent (CEDE) of 5.14{{e|−7}} ]s per ] (1.9{{e|3}} mrem/microcurie) for ingested <sup>210</sup>Po, this value is vital for working out the ] risk associated with <sup>210</sup>Po. For an assessment of ] effects (]) the dose rate (Gy day<sup>-1<sup>) is more important than the committed dose which is a dose inflicted over many years.<ref></ref> If the polonium is inhaled, the CEDE is even higher, 2.54{{e|-6}} Sv/Bq or 9.43{{e|3}} mrem/microcurie. | |||
{{cite journal|last1= Momoshima | first1 =N.|last2= Song | first2 = L. X.|last3= Osaki | first3 =S.|last4=Maeda | first4 =Y.| title = Biologically induced Po emission from fresh water | journal =J Environ Radioact| date = 2002 | volume = 63| issue = 2| pages= 187–197 | doi =10.1016/S0265-931X(02)00028-0| pmid =12363270| bibcode =2002JEnvR..63..187M}}</ref> This is similar to the way in which ], ], and ] are methylated in living things to create ] compounds. Studies investigating the metabolism of polonium-210 in rats have shown that only 0.002 to 0.009% of polonium-210 ingested is excreted as volatile polonium-210.<ref>{{cite journal |display-authors=4 |last1=Li |first1=Chunsheng |last2=Sadi |first2=Baki |last3=Wyatt |first3=Heather |last4=Bugden |first4=Michelle |last5=Priest |first5=Nicholas |last6=Wilkinson |first6=Diana |last7=Kramer |first7=Gary H. |date=2010 |title=Metabolism of <sup>210</sup>Po in rats: volatile <sup>210</sup>Po in excreta |journal=Radiation Protection Dosimetry |volume=140 |issue=2 |pages=158–162 |doi=10.1093/rpd/ncq047 |pmid=20159915}}</ref> | |||
===Acute effects=== | |||
In rats a dose of 1.45 MBq/kg of <sup>210</sup>Po tends to cause death in about 30 days.<ref>{{cite journal | |||
The ] (LD<sub>50</sub>) for acute radiation exposure is about 4.5 ].<ref name="pnl">{{cite web| url = http://www.pnl.gov/main/publications/external/technical_reports/PNNL-14424.pdf |title =Health Impacts from Acute Radiation Exposure| access-date = 2009-05-05|work=Pacific Northwest National Laboratory}}</ref> The ] <sup>210</sup>Po is 0.51 μSv/] if ingested, and 2.5 μSv/Bq if inhaled.<ref name="nsds">{{cite web| url = http://hpschapters.org/northcarolina/NSDS/210PoPDF.pdf |title =Nuclide Safety Data Sheet: Polonium–210| access-date = 2009-05-05|work=hpschapters.org}}</ref> A fatal 4.5 Sv dose can be caused by ingesting {{convert|8.8|MBq|μCi|abbr=on}}, about 50 ]s (ng), or inhaling {{convert|1.8|MBq|μCi|abbr=on}}, about 10 ng. One gram of <sup>210</sup>Po could thus in theory poison 20 million people, of whom 10 million would die. The actual toxicity of <sup>210</sup>Po is lower than these estimates because radiation exposure that is spread out over several weeks (the ] of polonium in humans is 30 to 50 days<ref>{{cite journal| osti =7162390 |title =Effective half-life of polonium in the human|author=Naimark, D.H.|date=1949-01-04|journal=Technical Report MLM-272/XAB, Mound Lab., Miamisburg, OH}}</ref>) is somewhat less damaging than an instantaneous dose. It has been estimated that a ] of <sup>210</sup>Po is {{convert|15|MBq|mCi}}, or 0.089 micrograms (μg), still an extremely small amount.<ref name="nuclearweaponsarchive">{{cite web| url =http://nuclearweaponarchive.org/News/PoloniumPoison.html |title =Polonium Poisoning|author=Carey Sublette|date=2006-12-14| access-date = 2009-05-05}}</ref><ref>{{cite journal| display-authors = 4| last1 = Harrison |first1=J. |title =Polonium-210 as a poison| date = 2007 |journal = J. Radiol. Prot.| pmid = 17341802 |volume = 27| issue = 1 | doi = 10.1088/0952-4746/27/1/001| quote = The conclusion is reached that 0.1–0.3 GBq or more absorbed to blood of an adult male is likely to be fatal within 1 month. This corresponds to ingestion of 1–3 GBq or more, assuming 10% absorption to blood |bibcode = 2007JRP....27...17H| pages = 17–40| last2 = Leggett| first2 = Rich| last3 = Lloyd| first3 = David| last4 = Phipps| first4 = Alan| last5 = Scott| first5 = Bobby| s2cid = 27764788 }}</ref> For comparison, one grain of ] is about 0.06 mg = 60 μg.<ref>{{cite web|url=http://www.physlink.com/Education/AskExperts/ae342.cfm|title=Approximately how many atoms are in a grain of salt?|author=Yasar Safkan|website=PhysLink.com: Physics & Astronomy}}</ref> | |||
| author = Rencováa J., Svoboda V., Holuša R., Volf V., Jones M. M., Singh P. K. | |||
| title = Reduction of subacute lethal radiotoxicity of polonium-210 in rats by chelating agents | |||
===Long term (chronic) effects=== | |||
| journal = International Journal of Radiation Biology | |||
In addition to the acute effects, radiation exposure (both internal and external) carries a long-term risk of death from cancer of 5–10% per Sv.<ref name="pnl" /> The general population is exposed to small amounts of polonium as a ] daughter in indoor air; the isotopes <sup>214</sup>Po and <sup>218</sup>Po are thought to cause the majority<ref>{{cite book| title = Health Risks of Radon and Other Internally Deposited Alpha-Emitters: BEIR IV|isbn=978-0-309-03789-1|page =5|publisher=National Academy Press|date=1988}}</ref> of the estimated 15,000–22,000 lung cancer deaths in the US every year that have been attributed to indoor radon.<ref>{{cite book| url =http://newton.nap.edu/html/beir6/ | archive-url =https://web.archive.org/web/20060919054314/http://newton.nap.edu/html/beir6/ | archive-date =2006-09-19 |title = Health Effects of Exposure to Indoor Radon| publisher=National Academy Press|place=Washington|date=1999}}</ref> ] causes additional exposure to polonium.<ref>{{cite web| url =https://www.straightdope.com/21343841/does-smoking-organically-grown-tobacco-lower-the-chance-of-lung-cancer |title =The Straight Dope: Does smoking organically grown tobacco lower the chance of lung cancer?| access-date = 2020-10-11|date =2007-09-28}}</ref> | |||
| volume = 72 | |||
| issue = 3 | |||
===Regulatory exposure limits and handling=== | |||
| pages = 247 - 249 | |||
The maximum allowable body burden for ingested <sup>210</sup>Po is only {{convert|1.1|kBq|nCi|abbr=on}}, which is equivalent to a particle massing only 6.8 picograms.<ref>{{Cite journal |last1=Boryło |first1=Alicja |last2=Skwarzec |first2=Bogdan |last3=Wieczorek |first3=Jarosław |date=2022-02-10 |title=Sources of polonium <sup>210</sup>Po and radio-lead <sup>210</sup>Pb in human body in Poland |journal=International Journal of Environmental Research and Public Health |language=en |volume=19 |issue=4 |pages=1984 |doi=10.3390/ijerph19041984 |doi-access=free |issn=1660-4601 |pmc=8872270 |pmid=35206170}}</ref> The maximum permissible workplace concentration of airborne <sup>210</sup>Po is about 10 Bq/m<sup>3</sup> ({{val|3|e=-10}} μCi/cm<sup>3</sup>).<ref>{{cite web |url = https://www.nrc.gov/reading-rm/doc-collections/cfr/part020/appb/Polonium-210.html |title = Nuclear Regulatory Commission limits for <sup>210</sup>Po| date = 2008-12-12 |access-date = 2009-01-12 |publisher = U.S. NRC}}</ref> The target organs for polonium in humans are the ] and ].<ref>{{cite web | url =http://www.pilgrimwatch.org/health1.html | title =PilgrimWatch – Pilgrim Nuclear – Health Impact | access-date =2009-05-05 | archive-url =https://web.archive.org/web/20090105192000/http://www.pilgrimwatch.org/health1.html | archive-date =2009-01-05 | url-status =dead }}</ref> As the spleen (150 g) and the liver (1.3 to 3 kg) are much smaller than the rest of the body, if the polonium is concentrated in these vital organs, it is a greater threat to life than the dose which would be suffered (on average) by the whole body if it were spread evenly throughout the body, in the same way as ] or ] (as T<sub>2</sub>O).<ref>{{cite journal| last1=Moroz|first1=B. B.| last2=Parfenov|first2=Yu. D.| year=1972| title=Metabolism and biological effects of polonium-210| journal=Atomic Energy Review| volume=10| issue=23| pages=175–232| url=https://inis.iaea.org/search/search.aspx?orig_q=RN:53061794}}</ref><ref>{{Cite journal |last1=Jefferson |first1=Robert D. |last2=Goans |first2=Ronald E. |last3=Blain |first3=Peter G. |last4=Thomas |first4=Simon H.L. |date=2009 |title=Diagnosis and treatment of polonium poisoning |url=http://www.tandfonline.com/doi/full/10.1080/15563650902956431 |journal=Clinical Toxicology |language=en |volume=47 |issue=5 |pages=379–392 |doi=10.1080/15563650902956431 |pmid=19492929 |issn=1556-3650}}</ref> | |||
| year = 1997 | |||
| doi = 10.1080/095530097143338 | |||
<sup>210</sup>Po is widely used in industry, and readily available with little regulation or restriction.<ref name="Zimmerman"/><ref>{{Cite journal|last1=Bastian|first1=R.K.|last2=Bachmaier|first2=J.T.|last3=Schmidt|first3=D.W.|last4=Salomon|first4=S.N.|last5=Jones|first5=A.|last6=Chiu|first6=W.A.|last7=Setlow|first7=L.W.|last8=Wolbarst|first8=A.W.|last9=Yu|first9=C.|date=2004-01-01|title=Radioactive Materials in Biosolids: National Survey, Dose Modeling & POTW Guidance|journal=Proceedings of the Water Environment Federation|volume=2004|issue=1|pages=777–803|doi=10.2175/193864704784343063| url=https://www.researchgate.net/publication/314571422}}</ref> In the US, a tracking system run by the Nuclear Regulatory Commission was implemented in 2007 to register purchases of more than {{convert|16|Ci}} of polonium-210 (enough to make up 5,000 lethal doses). The IAEA "is said to be considering tighter regulations ... There is talk that it might tighten the polonium reporting requirement by a factor of 10, to {{convert|1.6|Ci}}."<ref name="Zimmerman">{{cite news |url=https://www.nytimes.com/2006/12/19/opinion/19zimmerman.html |title=Opinion: The Smoky Bomb Threat |access-date=2006-12-19 |newspaper=The New York Times |first=Peter D. |last=Zimmerman|date=2006-12-19}}</ref> As of 2013, this is still the only alpha emitting byproduct material available, as a NRC Exempt Quantity, which may be held without a radioactive material license.{{citation needed|date=September 2013}} | |||
Polonium and its compounds must be handled with caution inside special alpha ]es, equipped with ] filters and continuously maintained under depression to prevent the radioactive materials from leaking out. Gloves made of ] (]) do not properly withstand chemical attacks, a.o. by concentrated ] {{nowrap|(e.g., 6 M {{chem2|HNO3}})}} commonly used to keep polonium in ] while minimizing its ] onto glass. They do not provide sufficient protection against the contamination from polonium (] of <sup>210</sup>Po solution through the intact latex membrane, or worse, direct contact through tiny holes and cracks produced when the latex begins to suffer degradation by acids or UV from ambient light); additional surgical gloves are necessary (inside the glovebox to protect the main gloves when handling strong acids and bases, and also from outside to protect the operator hands against <sup>210</sup>Po contamination from diffusion, or direct contact through glove defects). Chemically more resistant, and also denser, ] and butyl gloves shield alpha particles emitted by polonium better than natural rubber.<ref>], p. 204.</ref> The use of natural rubber gloves is not recommended for handling <sup>210</sup>Po solutions. | |||
===Cases of poisoning=== | |||
Despite the element's highly hazardous properties, circumstances in which polonium poisoning can occur are rare. Its extreme scarcity in nature,<ref>{{Cite journal |last1=Hussain |first1=N. |last2=Ferdelman |first2=T. G. |last3=Church |first3=T. M. |last4=Luther |first4=George W. |date=1995 |title=Bio-volatilization of polonium: Results from laboratory analyses |url=https://www.researchgate.net/publication/226970567 |journal=Aquatic Geochemistry |language=en |volume=1 |issue=2 |pages=175–188 |doi=10.1007/BF00702890 |bibcode=1995AqGeo...1..175H |issn=1380-6165}}</ref> the short half-lives of all its isotopes, the specialised facilities and equipment needed to obtain any significant quantity, and safety precautions against laboratory accidents all make harmful exposure events unlikely. As such, only a handful of cases of radiation poisoning specifically attributable to polonium exposure have been confirmed.<ref>{{Cite journal |last1=Nathwani |first1=Amit C |last2=Down |first2=James F |last3=Goldstone |first3=John |last4=Yassin |first4=James |last5=Dargan |first5=Paul I |last6=Virchis |first6=Andres |last7=Gent |first7=Nick |last8=Lloyd |first8=David |last9=Harrison |first9=John D |date=2016 |title=Polonium-210 poisoning: a first-hand account |url=https://linkinghub.elsevier.com/retrieve/pii/S0140673616001446 |journal=The Lancet |language=en |volume=388 |issue=10049 |pages=1075–1080 |doi=10.1016/S0140-6736(16)00144-6|pmid=27461439 }}</ref> | |||
====20th century==== | |||
In response to concerns about the risks of occupational polonium exposure, quantities of <sup>210</sup>Po were administered to five human volunteers at the University of Rochester from 1944 to 1947, in order to study its biological behaviour. These studies were funded by the ] and the AEC. Four men and a woman participated, all suffering from terminal cancers, and ranged in age from their early thirties to early forties; all were chosen because experimenters wanted subjects who had not been exposed to polonium either through work or accident.<ref name="Rochester">{{cite journal |last1=Moss |first1=William |last2=Eckhardt |first2=Roger |date=1995 |title=The human plutonium injection experiments |url=https://fas.org/sgp/othergov/doe/lanl/pubs/00326640.pdf |journal=Los Alamos Science |volume=23 |pages=177–233}}</ref> <sup>210</sup>Po was injected into four hospitalised patients, and orally given to a fifth. None of the administered doses (all ranging from 0.17 to 0.30 μ] kg<sup>−1</sup>) approached fatal quantities.<ref>{{cite book |last=Fink |first=Robert |date=1950 |title=Biological studies with polonium, radium, and plutonium |publisher=McGraw-Hill |series=National Nuclear Energy Series |volume=VI-3 |isbn=5-86656-114-X |language=ru}}</ref><ref name="Rochester" /> | |||
The first documented death directly resulting from polonium poisoning occurred in the ], on 10 July 1954.<ref name="Gasteva">{{cite book |last=Gasteva |first=G. N. |date=2001 |editor-last=Ilʹin |editor-first=L. A. |title=Radiacionnaja medicina: rukovodstvo dlja vračej-issledovatelej i organizatorov zdravooxranenija, Tom 2 (Radiacionnye poraženija čeloveka) |trans-title=Radiation medicine: a guide for medical researchers and healthcare managers, Volume 2 (Radiation damage to humans) |publisher=IzdAT |pages=99–107 |chapter=Ostraja lučevaja boleznʹ ot postuplenija v organizm polonija |trans-chapter=Acute radiation sickness by ingestion of polonium into the body |isbn=5-86656-114-X |language=ru}}</ref><ref>{{cite journal |last1=Harrison |first1=John |last2=Leggett |first2=Rich |last3=Lloyd |first3=David |last4=Phipps |first4=Alan |last5=Scott |first5=Bobby |date=2 March 2007 |title=Polonium-210 as a poison |journal=Journal of Radiological Protection |volume=27 |issue=1 |pages=17–40 |doi=10.1088/0952-4746/27/1/001|pmid=17341802 |bibcode=2007JRP....27...17H |s2cid=27764788 }}</ref> An unidentified 41-year-old man presented for medical treatment on 29 June, with severe vomiting and fever; the previous day, he had been working for five hours in an area in which, unknown to him, a capsule containing <sup>210</sup>Po had depressurised and begun to disperse in aerosol form. Over this period, his total intake of airborne <sup>210</sup>Po was estimated at 0.11 GBq (almost 25 times the estimated LD<sub>50</sub> by inhalation of 4.5 MBq). Despite treatment, his condition continued to worsen and he died 13 days after the exposure event.<ref name="Gasteva" /> | |||
From 1955 to 1957 the ] had been releasing polonium-210. The ] brought the need for testing of the land downwind for radioactive material contamination, and this is how it was found. An estimate of 8.8 terabecquerels (240 Ci) of polonium-210 has been made. | |||
It has also been suggested that ]'s 1956 death from leukaemia was owed to the radiation effects of polonium. She was accidentally exposed in 1946 when a sealed capsule of the element exploded on her laboratory bench.<ref>{{cite news|url=http://www.news.com.au/dailytelegraph/story/0,22049,20863878-5001031,00.html |title=Innocent chemical a killer |publisher=The Daily Telegraph (Australia) |date=2006-12-04 |access-date=2009-05-05 |first=Jeremy |last=Manier |url-status=dead |archive-url=https://web.archive.org/web/20090106013604/http://www.news.com.au/dailytelegraph/story/0,22049,20863878-5001031,00.html |archive-date=January 6, 2009 }}</ref> | |||
As well, several deaths in Israel during 1957–1969 have been alleged to have resulted from <sup>210</sup>Po exposure.<ref>{{cite book|last = Karpin|first = Michael|title = The bomb in the basement: How Israel went nuclear and what that means for the world|publisher = Simon and Schuster|date = 2006|isbn = 978-0-7432-6594-2|url = https://archive.org/details/bombinbasementho00karp}}</ref> A leak was discovered at a ] laboratory in 1957. Traces of <sup>210</sup>Po were found on the hands of Professor Dror Sadeh, a physicist who researched radioactive materials. Medical tests indicated no harm, but the tests did not include bone marrow. Sadeh, one of his students, and two colleagues died from various ]s over the subsequent few years. The issue was investigated secretly, but there was never any formal admission of a connection between the leak and the deaths.<ref name='LA Times 2007-01-01'>{{cite news |first=Thomas |last=Maugh |author2=Karen Kaplan |title=A restless killer radiates intrigue |date=2007-01-01|url =https://www.latimes.com/archives/la-xpm-2007-jan-01-sci-polonium1-story.html |work =Los Angeles Times |access-date = 2008-09-17}}</ref> | |||
The ] July 16, 1979 is reported to have released ]. The report states animals had higher concentrations of lead-210, polonium-210 and radium-226 than the tissues from control animals.<ref name="Millard1983">{{cite web | author= Jere Millard, Bruce Gallaher, David Baggett, Steven Gary | date=September 1983 | title=The Church Rock uranium mill tailings spill a health and environmental assessment, page 32 | url=https://semspub.epa.gov/work/06/1000720.pdf | access-date=2024-01-30}}</ref> | |||
====21st century==== | |||
{{Further|Poisoning of Alexander Litvinenko|Cause of Yasser Arafat's death}} | |||
The cause of the ] of ], a former Russian ] agent who had defected to the United Kingdom in 2001, was identified to be poisoning with a lethal dose of <sup>210</sup>Po;<ref>{{cite news |title=The mystery of Litvinenko's death |url=http://news.bbc.co.uk/1/hi/uk/6180432.stm |date=2006-11-24 |work=BBC News |first=Tom |last=Geoghegan}}</ref><ref name="bbc">{{cite news| url =http://news.bbc.co.uk/1/hi/uk/6698545.stm |title = UK requests Lugovoi extradition| access-date = 2009-05-05|work=BBC News|date=2007-05-28}}</ref> it was subsequently determined that the <sup>210</sup>Po had probably been deliberately administered to him by two Russian ex-security agents, ] and ].<ref>{{cite web|url=https://www.litvinenkoinquiry.org/report|publisher=The Litvinenko Inquiry|title=Report|access-date=21 January 2016}}</ref><ref>{{cite news|last1=Addley|first1=Esther|last2=Harding|first2=Luke|title=Litvinenko 'probably murdered on personal orders of Putin'|url=https://www.theguardian.com/world/2016/jan/21/alexander-litvinenko-was-probably-murdered-on-personal-orders-of-putin|access-date=21 January 2016|work=The Guardian|date=21 January 2016}}</ref> As such, Litvinenko's death was the first (and, to date, only) confirmed instance in which polonium's extreme toxicity has been used with malicious intent.<ref>{{cite news |first=Steve |last=Boggan |title=Who else was poisoned by polonium? |work=] |date=5 June 2007 |url=https://www.theguardian.com/world/2007/jun/05/russia.science |access-date=28 August 2021}}</ref><ref name="PoAlJazeera">{{cite news |first=David |last=Poort |title=Polonium: a silent killer |work=Al Jazeera News |date=6 November 2013 |url=https://www.aljazeera.com/news/2013/11/6/polonium-a-silent-killer |access-date=28 August 2021}}</ref><ref>{{cite journal |last1=Froidevaux |first1=Pascal |last2=Bochud |first2=François |last3=Baechler |first3=Sébastien |last4=Castella |first4=Vincent |last5=Augsburger |first5=Marc |last6=Bailat |first6=Claude |last7=Michaud |first7=Katarzyna |last8=Straub |first8=Marietta |last9=Pecchia |first9=Marco |last10=Jenk |first10=Theo M. |last11=Uldin |first11=Tanya |last12=Mangin |first12=Patrice |date=February 2016 |title=²¹⁰Po poisoning as possible cause of death: forensic investigations and toxicological analysis of the remains of Yasser Arafat |journal=Forensic Science International |volume=259 |pages=1–9 |doi=10.1016/j.forsciint.2015.09.019 |pmid=26707208 |s2cid=207751390 |doi-access=free }}</ref> | |||
In 2011, an allegation surfaced that the death of ] leader ], who died on 11 November 2004 of uncertain causes, also resulted from deliberate polonium poisoning,<ref>{{cite news|date=17 January 2011|title=الأخبار – ضابط فلسطيني: خصوم عرفات قتلوه عربي|publisher=]|url=http://www.aljazeera.net/news/pages/676ce5b7-f085-45d4-9c97-5c7a32864c06|url-status=dead|access-date=2021-06-05|archive-url=https://web.archive.org/web/20120704225411/http://www.aljazeera.net/news/pages/676ce5b7-f085-45d4-9c97-5c7a32864c06|archive-date=2012-07-04}}</ref><ref>{{cite episode |title=George Galloway and Alex Goldfarb on Litvinenko inquiry |url=https://www.youtube.com/watch?v=H0om8ii5XVs&t=113 | archive-url=https://ghostarchive.org/varchive/youtube/20211030/H0om8ii5XVs| archive-date=2021-10-30|series=] |network=] |date=21 January 2016 |time=1:53 |access-date=28 March 2018}}{{cbignore}}</ref> and in July 2012, concentrations of <sup>210</sup>Po many times more than normal were detected in Arafat's clothes and personal belongings by the Institut de Radiophysique in Lausanne, Switzerland.<ref>{{Cite journal | last1 = Froidevaux | first1 = P. | last2 = Baechler | first2 = S. B. | last3 = Bailat | first3 = C. J. | last4 = Castella | first4 = V. | last5 = Augsburger | first5 = M. | last6 = Michaud | first6 = K. | last7 = Mangin | first7 = P. | last8 = Bochud | first8 = F. O. O. | doi = 10.1016/S0140-6736(13)61834-6 | title = Improving forensic investigation for polonium poisoning | journal = The Lancet | volume = 382 | issue = 9900 | pages = 1308 | year = 2013 | pmid = 24120205| s2cid = 32134286}}</ref><ref name="BartReuters">Bart, Katharina (2012-07-03). {{Webarchive|url=https://web.archive.org/web/20151007125548/http://www.reuters.com/article/2012/07/03/us-palestinians-arafat-idUSBRE8621CL20120703 |date=2015-10-07 }}. Reuters.</ref> Even though Arafat's symptoms were acute gastroenteritis with diarrhoea and vomiting,<ref name="NBC News">{{cite news |last1=Paul Taylor |title=Palestinian leader Yasser Arafat was murdered with polonium: widow |url=https://www.nbcnews.com/news/world/palestinian-leader-yasser-arafat-was-murdered-polonium-widow-flna8C11542188 |work=NBC News |agency=Reuters |date=Nov 7, 2013}}</ref> the institute's spokesman said that despite the tests the symptoms described in Arafat's medical reports were not consistent with <sup>210</sup>Po poisoning, and conclusions could not be drawn.<ref name="BartReuters" /> In 2013 the team found levels of polonium in Arafat's ribs and pelvis 18 to 36 times the average,<ref name=AJ_Swiss_study>{{Cite web|last2=Silverstein|first1=David | last1=Poort| first2=Ken |title=Swiss study: Polonium found in Arafat's bones|url=https://www.aljazeera.com/news/2013/11/7/swiss-study-polonium-found-in-arafats-bones|access-date=12 February 2023 |publisher=www.aljazeera.com| date = 6 November 2013 |language=en}}</ref><ref name=Reuters_Arafat_poisoned>{{Cite news|title=Swiss Team: Arafat Poisoned to Death With Polonium |language=en|work=Haaretz|url=https://www.haaretz.com/2013-11-06/ty-article/swiss-team-arafat-poisoned-with-polonium/0000017f-e386-d7b2-a77f-e3876db50000 | date= 6 November 2013 |access-date=12 February 2023}}</ref> even though by this point in time the amount had diminished by a factor of 2 million.<ref name=LT24.05.14>{{in lang|fr}} Luis Lema, , '']'', Saturday 24 May 2014, p. 3.</ref> Forensic scientist Dave Barclay stated, "In my opinion, it is absolutely certain that the cause of his illness was polonium poisoning. ... What we have got is the smoking gun - the thing that caused his illness and was given to him with malice."<ref name="NBC News"/><ref name=AJ_Swiss_study/> Subsequently, French and Russian teams claimed that the elevated <sup>210</sup>Po levels were not the result of deliberate poisoning, and did not cause Arafat's death.<ref name="autogenerated1">Isachenkov, Vadim (2013-12-27) . Associated Press.</ref><ref>{{cite news|date=3 December 2013|title=Arafat did not die of poisoning, French tests conclude|publisher=]|url=https://www.reuters.com/article/us-palestinians-arafat-idUKBRE9B20DI20131203|access-date=1 September 2021}}</ref> | |||
It has also been suspected that Russian businessman ] was killed with polonium. He had symptoms similar to Aleksander Litvinenko.<ref name=timesonline>{{Cite news|url=https://www.thetimes.co.uk/article/the-putin-bodyguard-riddle-687f9vcdmzf|title=The Putin bodyguard riddle|date=3 December 2006|newspaper=The Sunday Times}}</ref> | |||
===Treatment=== | |||
It has been suggested that ], such as British anti-Lewisite (]), can be used to decontaminate humans.<ref>{{cite web| url = https://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/ucm071944.pdf |title = Guidance for Industry. Internal Radioactive Contamination — Development of Decorporation Agents| access-date = 2009-07-07|work=US Food and Drug Administration}}</ref> In one experiment, rats were given a fatal dose of 1.45 MBq/kg (8.7 ng/kg) of <sup>210</sup>Po; | |||
all untreated rats were dead after 44 days, but 90% of the rats treated with the chelation agent | |||
HOEtTTC remained alive for five months.<ref>{{cite journal | |||
|display-authors = 4 | |||
|author = Rencováa J. | |||
|author2 = Svoboda V. | |||
|author3 = Holuša R. | |||
|author4 = Volf V. | |||
|author5 = Jones M. M. | |||
|author6 = Singh P. K. | |||
|title = Reduction of subacute lethal radiotoxicity of polonium-210 in rats by chelating agents | |||
|journal = International Journal of Radiation Biology | |||
|volume = 72 | |||
|issue = 3 | |||
|pages = 341–8 | |||
|date = 1997 | |||
|doi = 10.1080/095530097143338 | |||
|pmid = 9298114 | |||
}}</ref> | }}</ref> | ||
===Detection in biological specimens=== | |||
The maximum allowable body burden for ingested polonium is only 1,100 ] (0.03 microcurie), which is equivalent to a particle weighing only 6.8 × 10<sup>-12</sup> gram. Weight for weight, polonium is approximately 2.5 × 10<sup>11</sup> (250 billion) times as toxic as ]. The maximum permissible concentration for airborne soluble polonium compounds is about 7,500 Bq/m<sup>3</sup> (2 × 10<sup>-11</sup> µCi/cm<sup>3</sup>). The ] of polonium in humans is 30 to 50 days.<ref></ref> | |||
Polonium-210 may be quantified in biological specimens by alpha particle spectrometry to confirm a diagnosis of poisoning in hospitalized patients or to provide evidence in a medicolegal death investigation. The baseline urinary excretion of polonium-210 in healthy persons due to routine exposure to environmental sources is normally in a range of 5–15 mBq/day. Levels in excess of 30 mBq/day are suggestive of excessive exposure to the radionuclide.<ref>Baselt, R. {{Webarchive|url=https://web.archive.org/web/20130616021325/http://www.biomedicalpublications.com/dt10.pdf |date=2013-06-16 }}, 10th edition, Biomedical Publications, Seal Beach, CA.</ref> | |||
===Occurrence in humans and the biosphere=== | |||
Notably the death in 2006 of ] has been announced as probably due to Polonium poisoning.<ref>{{cite news | title=The mystery of Litvinenko's death |url=http://news.bbc.co.uk/1/hi/uk/6180432.stm | date=24 November 2006 | publisher=BBC News}}</ref> | |||
Polonium-210 is widespread in the ], including in human tissues, because of its position in the ]. Natural ] in the ] decays through a series of solid radioactive intermediates including ] to the radioactive noble gas ], some of which, during its 3.8-day half-life, diffuses into the atmosphere. There it decays through several more steps to polonium-210, much of which, during its 138-day half-life, is washed back down to the Earth's surface, thus entering the biosphere, before finally decaying to stable ].<ref>{{cite journal|doi =10.1038/187211a0|pmid =13852349|title =Lead-210 and Polonium-210 in Grass|date =1960|last1 =Hill|first1 = C. R.|journal =Nature|volume =187|issue =4733|pages =211–212|bibcode = 1960Natur.187..211H|s2cid =4261294}}</ref><ref>{{cite journal|last = Hill|first = C. R.| date =1963|title = Natural occurrence of unsupported radium-F (Po-210) in tissue|journal = Health Physics|volume = 9|pages = 952–953|pmid = 14061910}}</ref><ref>{{cite journal|doi = 10.1007/BF00398136 |title = Polonium-210 and lead-210 in marine food chains|date = 1979|last1 = Heyraud|first1 = M.|last2 = Cherry|first2 = R. D.|journal = Marine Biology |volume = 52 |issue = 3 |pages = 227–236| bibcode=1979MarBi..52..227H |s2cid = 58921750}}</ref> | |||
{{further|]}} | |||
As early as the 1920s, French biologist ], using polonium provided by his colleague ], showed that the element has a specific pattern of uptake in rabbit tissues, with high concentrations, particularly in ], ], and ].<ref>Lacassagne, A. & Lattes, J. (1924) ''Bulletin d'Histologie Appliquée à la Physiologie et à la Pathologie'', '''1''', 279.</ref> More recent evidence suggests that this behavior results from polonium substituting for its congener sulfur, also in group 16 of the periodic table, in sulfur-containing amino-acids or related molecules<ref>{{cite journal|jstor = 3577929|pages = 379–382|last1 = Vasken Aposhian|first1 = H.|last2 = Bruce|first2 = D. C.|title = Binding of Polonium-210 to Liver Metallothionein|volume = 126|issue = 3 |journal = Radiation Research |date = 1991 |doi = 10.2307/3577929 |pmid = 2034794|bibcode = 1991RadR..126..379A}}</ref> and that similar patterns of distribution occur in human tissues.<ref>{{cite journal |pmid = 5867584 |date = 1965 |last1 = Hill|first1 = C. R.|title = Polonium-210 in man|volume = 208|issue = 5009|pages = 423–8|journal = Nature |doi = 10.1038/208423a0|bibcode = 1965Natur.208..423H|s2cid = 4215661 }}</ref> Polonium is indeed an element naturally present in all humans, contributing appreciably to natural background dose, with wide geographical and cultural variations, and particularly high levels in arctic residents, for example.<ref>{{cite journal|doi = 10.1126/science.152.3726.1261 |title = Polonium-210 Content of Human Tissues in Relation to Dietary Habit|date = 1966|last1 = Hill|first1 = C. R.|journal = Science |volume = 152|issue = 3726|pages = 1261–2|pmid = 5949242 |bibcode = 1966Sci...152.1261H|s2cid = 33510717}}</ref> | |||
===Tobacco=== | |||
] in tobacco contributes to many of the cases of ] worldwide. Most of this polonium is derived from ] deposited on tobacco leaves from the atmosphere; the lead-210 is a product of ] gas, much of which appears to originate from the decay of ] from fertilizers applied to the tobacco soils.<ref name="Muggli08" /><ref name="Martell1974">{{cite journal|last1=Martell|first1=E. A.|title=Radioactivity of tobacco trichomes and insoluble cigarette smoke particles|journal=Nature|date=1974|volume=249|issue=5454|pages=214–217|doi=10.1038/249215a0|pmid=4833238|bibcode=1974Natur.249..215M|s2cid=4281866}}</ref><ref name="Martell1975">{{cite journal|last1=Martell|first1=E. A.|title=Tobacco Radioactivity and Cancer in Smokers: Alpha interactions with chromosomes of cells surrounding insoluble radioactive smoke particles may cause cancer and contribute to early atherosclerosis development in cigarette smokers|journal=American Scientist|date=1975|volume=63|issue=4|pages=404–412|jstor=27845575|bibcode = 1975AmSci..63..404M |pmid=1137236}}</ref><ref>{{cite journal|journal=Journal of the Royal Society of Medicine|volume= 101|issue= 3|pages= 156–7|title= The big idea: polonium, radon and cigarettes|doi=10.1258/jrsm.2007.070021 |pmid= 18344474|pmc= 2270238|year= 2008|last1= Tidd|first1= M. J.}}</ref><ref>Birnbauer, William (2008-09-07) . ''The Age'', Melbourne, Australia</ref> | |||
The presence of polonium in tobacco smoke has been known since the early 1960s.<ref>{{cite journal| author = Radford EP Jr| author2 = Hunt VR |title = Polonium 210: a volatile radioelement in cigarettes |journal = Science| date =1964| volume = 143| issue = 3603 | doi = 10.1126/science.143.3603.247| pmid=14078362| bibcode=1964Sci...143..247R| pages = 247–9| s2cid = 23455633 }}</ref><ref>{{cite journal| author = Kelley TF| title = Polonium 210 content of mainstream cigarette smoke| journal = Science| date =1965| volume =149| issue = 3683| pages = 537–538| doi = 10.1126/science.149.3683.537 | pmid = 14325152|bibcode = 1965Sci...149..537K| s2cid = 22567612}}</ref> Some of the world's biggest tobacco firms researched ways to remove the substance—to no avail—over a 40-year period. The results were never published.<ref name="Muggli08" /> | |||
===Food=== | |||
Polonium is found in the food chain, especially in seafood.<ref>{{cite journal|display-authors = 4|author = Ota, Tomoko|author2 = Sanada, Tetsuya|author3 = Kashiwara, Yoko|author4 = Morimoto, Takao|author5 = Sato, Kaneaki|name-list-style = amp|journal = Japanese Journal of Health Physics|date = 2009|volume = 44|title = Evaluation for Committed Effective Dose Due to Dietary Foods by the Intake for Japanese Adults| issue=1 |url = http://ci.nii.ac.jp/naid/110007226760|doi = 10.5453/jhps.44.80|pages = 80–88|doi-access = free}}</ref><ref>{{cite journal|author = Smith-Briggs, JL|author2 = Bradley, EJ|journal =Science of the Total Environment |date=1984 |volume=35 |title=Measurement of natural radionuclides in U.K. diet |pmid=6729447 |issue=3 |pages=431–40|doi = 10.1016/0048-9697(84)90015-9|bibcode=1984ScTEn..35..431S}}</ref> | |||
==See also== | ==See also== | ||
* ] | * ] | ||
* ] | |||
* The entry for polonium at ] | |||
* ] | |||
== |
==References== | ||
{{Reflist|30em}} | |||
<div class="references-small"><references /></div> | |||
==Bibliography== | |||
== External links == | |||
* {{cite book |title=Advances in Inorganic Chemistry and Radiochemistry |chapter=The Chemistry of Polonium |ref=Bagnall|last1=Bagnall |first1=K. W. |date=1962 |publisher=] |location=New York |isbn=978-0-12-023604-6|doi=10.1016/S0065-2792(08)60268-X|pages=197–226 |access-date=June 14, 2012 |chapter-url=https://books.google.com/books?id=8qePsa3V8GQC&pg=PA212|volume=4}} | |||
* {{cite book|ref=Greenwood|author=Greenwood, Norman N.|author2=Earnshaw, Alan |date=1997|title= Chemistry of the Elements|edition= 2nd|publisher= Butterworth–Heinemann|isbn=978-0080379418}} | |||
==External links== | |||
{{Commons|Polonium}} | {{Commons|Polonium}} | ||
{{ |
{{Wiktionary|Polonium}} | ||
* at '']'' (University of Nottingham) | |||
References and External links verified ] unless noted. | |||
* | |||
* | |||
* | |||
* | |||
{{Periodic table (navbox)}} | |||
{{Polonium compounds}} | |||
{{Marie & Pierre Curie}} | |||
{{Authority control}} | |||
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Latest revision as of 14:20, 5 December 2024
Not to be confused with Plutonium.Chemical element with atomic number 84 (Po)
Polonium is a chemical element; it has symbol Po and atomic number 84. A rare and highly radioactive metal (although sometimes classified as a metalloid) with no stable isotopes, polonium is a chalcogen and chemically similar to selenium and tellurium, though its metallic character resembles that of its horizontal neighbors in the periodic table: thallium, lead, and bismuth. Due to the short half-life of all its isotopes, its natural occurrence is limited to tiny traces of the fleeting polonium-210 (with a half-life of 138 days) in uranium ores, as it is the penultimate daughter of natural uranium-238. Though longer-lived isotopes exist, such as the 124 years half-life of polonium-209, they are much more difficult to produce. Today, polonium is usually produced in milligram quantities by the neutron irradiation of bismuth. Due to its intense radioactivity, which results in the radiolysis of chemical bonds and radioactive self-heating, its chemistry has mostly been investigated on the trace scale only.
Polonium was discovered on July 18, 1898 by Marie Skłodowska-Curie and Pierre Curie, when it was extracted from the uranium ore pitchblende and identified solely by its strong radioactivity: it was the first element to be discovered in this way. Polonium was named after Marie Skłodowska-Curie's homeland of Poland, which at the time was partitioned between three countries. Polonium has few applications, and those are related to its radioactivity: heaters in space probes, antistatic devices, sources of neutrons and alpha particles, and poison (e.g., poisoning of Alexander Litvinenko). It is extremely dangerous to humans.
Characteristics
Po is an alpha emitter that has a half-life of 138.4 days; it decays directly to its stable daughter isotope, Pb. A milligram (5 curies) of Po emits about as many alpha particles per second as 5 grams of Ra, which means it is 5,000 times more radioactive than radium. A few curies (1 curie equals 37 gigabecquerels, 1 Ci = 37 GBq) of Po emit a blue glow which is caused by ionisation of the surrounding air.
About one in 100,000 alpha emissions causes an excitation in the nucleus which then results in the emission of a gamma ray with a maximum energy of 803 keV.
Solid state form
Polonium is a radioactive element that exists in two metallic allotropes. The alpha form is the only known example of a simple cubic crystal structure in a single atom basis at STP (space group Pm3m, no. 221). The unit cell has an edge length of 335.2 picometers; the beta form is rhombohedral. The structure of polonium has been characterized by X-ray diffraction and electron diffraction.
Po has the ability to become airborne with ease: if a sample is heated in air to 55 °C (131 °F), 50% of it is vaporized in 45 hours to form diatomic Po2 molecules, even though the melting point of polonium is 254 °C (489 °F) and its boiling point is 962 °C (1,764 °F). More than one hypothesis exists for how polonium does this; one suggestion is that small clusters of polonium atoms are spalled off by the alpha decay.
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 acids but is only slightly soluble in alkalis. Polonium solutions are first colored in pink by the Po ions, but then rapidly become yellow because alpha radiation from polonium ionizes the solvent and converts Po into Po. As polonium also emits alpha-particles after disintegration so this process is accompanied by bubbling and emission of heat and light by glassware due to the absorbed alpha particles; as a result, polonium solutions are volatile and will evaporate within days unless sealed. At pH about 1, polonium ions are readily hydrolyzed and complexed by acids such as oxalic acid, citric acid, and tartaric acid.
Compounds
Polonium has no common compounds, and almost all of its compounds are synthetically created; more than 50 of those are known. The most stable class of polonium compounds are polonides, which are prepared by direct reaction of two elements. Na2Po has the antifluorite structure, the polonides of Ca, Ba, Hg, Pb and lanthanides form a NaCl lattice, BePo and CdPo have the wurtzite and MgPo the nickel arsenide structure. Most polonides decompose upon heating to about 600 °C, except for HgPo that decomposes at ~300 °C and the lanthanide polonides, which do not decompose but melt at temperatures above 1000 °C. For example, the polonide of praseodymium (PrPo) melts at 1250 °C, and that of thulium (TmPo) melts at 2200 °C. PbPo is one of the very few naturally occurring polonium compounds, as polonium alpha decays to form lead.
Polonium hydride (PoH
2) is a volatile liquid at room temperature prone to dissociation; it is thermally unstable. 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, PoO, PoO2 and PoO3, are the products of oxidation of polonium.
Halides of the structure PoX2, PoX4 and PoF6 are known. They are soluble in the corresponding hydrogen halides, i.e., PoClX in HCl, PoBrX in HBr and PoI4 in HI. Polonium dihalides are formed by direct reaction of the elements or by reduction of PoCl4 with SO2 and with PoBr4 with H2S at room temperature. Tetrahalides can be obtained by reacting polonium dioxide with HCl, HBr or HI.
Other polonium compounds include the polonite, potassium polonite; various polonate solutions; and the acetate, bromate, carbonate, citrate, chromate, cyanide, formate, (II) or (IV) hydroxide, nitrate, selenate, selenite, monosulfide, sulfate, disulfate or sulfite salts.
A limited organopolonium chemistry is known, mostly restricted to dialkyl and diaryl polonides (R2Po), triarylpolonium halides (Ar3PoX), and diarylpolonium dihalides (Ar2PoX2). Polonium also forms soluble compounds with some ligands, such as 2,3-butanediol and thiourea.
Formula | Color | m.p. (°C) | Sublimation temp. (°C) |
Symmetry | Pearson symbol | Space group | No | a (pm) | b(pm) | c(pm) | Z | ρ (g/cm) | ref |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
PoO | black | ||||||||||||
PoO2 | pale yellow | 500 (dec.) | 885 | fcc | cF12 | Fm3m | 225 | 563.7 | 563.7 | 563.7 | 4 | 8.94 | |
PoH2 | -35.5 | ||||||||||||
PoCl2 | dark ruby red | 355 | 130 | orthorhombic | oP3 | Pmmm | 47 | 367 | 435 | 450 | 1 | 6.47 | |
PoBr2 | purple-brown | 270 (dec.) | |||||||||||
PoCl4 | yellow | 300 | 200 | monoclinic | |||||||||
PoBr4 | red | 330 (dec.) | fcc | cF100 | Fm3m | 225 | 560 | 560 | 560 | 4 | |||
PoI4 | black |
Oxides |
Hydrides |
|
Isotopes
Main article: Isotopes of poloniumPolonium has 42 known isotopes, all of which are radioactive. They have atomic masses that range from 186 to 227 u. Po (half-life 138.376 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 U. The longer-lived Po (half-life 124 years, longest-lived of all polonium isotopes) and Po (half-life 2.9 years) can be manufactured through the alpha, proton, or deuteron bombardment of lead or bismuth in a cyclotron.
History
Tentatively called "radium F", polonium was discovered by Marie and Pierre Curie in July 1898, and was named after Marie Curie's native land of Poland (Latin: Polonia). Poland at the time was under Russian, German, and Austro-Hungarian partition, and did not exist as an independent country. It was Curie's hope that naming the element after her native land would publicize its lack of independence. Polonium may be the first element named to highlight a political controversy.
This element was the first one discovered by the Curies while they were investigating the cause of pitchblende radioactivity. Pitchblende, after removal of the radioactive elements uranium and thorium, was more radioactive than the uranium and thorium combined. This spurred the Curies to search for additional radioactive elements. They first separated out polonium from pitchblende in July 1898, and five months later, also isolated radium. German scientist Willy Marckwald successfully isolated 3 milligrams of polonium in 1902, though at the time he believed it was a new element, which he dubbed "radio-tellurium", and it was not until 1905 that it was demonstrated to be the same as polonium.
In the United States, polonium was produced as part of the Manhattan Project's Dayton Project during World War II. Polonium and beryllium were the key ingredients of the 'Urchin' initiator at the center of the bomb's spherical pit. 'Urchin' initiated the nuclear chain reaction at the moment of prompt-criticality to ensure that the weapon did not fizzle. 'Urchin' was used in early U.S. weapons; subsequent U.S. weapons utilized a pulse neutron generator for the same purpose.
Much of the basic physics of polonium was classified until after the war. The fact that a polonium-beryllium (Po-Be) initiator was used in the gun-type nuclear weapons was classified until the 1960s.
The Atomic Energy Commission and the Manhattan Project funded human experiments using polonium on five people at the University of Rochester between 1943 and 1947. The people were administered between 9 and 22 microcuries (330 and 810 kBq) of polonium to study its excretion.
Occurrence and production
Polonium is a very rare element in nature because of the short half-lives of all its isotopes. Nine isotopes, from 210 to 218 inclusive, occur in traces as decay products: Po, Po, and Po occur in the decay chain of U; Po and Po occur in the decay chain of U; Po and Po occur in the decay chain of Th; and Po and Po occur in the decay chain of Np. (No primordial Np survives, but traces of it are continuously regenerated through (n,2n) knockout reactions in natural U.) Of these, Po is the only isotope with a half-life longer than 3 minutes.
Polonium can be found in uranium ores at about 0.1 mg per metric ton (1 part in 10), which is approximately 0.2% of the abundance of radium. The amounts in the Earth's crust are not harmful. Polonium has been found in tobacco smoke from tobacco leaves grown with phosphate fertilizers.
Because it is present in small concentrations, isolation of polonium from natural sources is a tedious process. The largest batch of the element ever extracted, performed in the first half of the 20th century, contained only 40 Ci (1.5 TBq) (9 mg) of polonium-210 and was obtained by processing 37 tonnes of residues from radium production. Polonium is now usually obtained by irradiating bismuth with high-energy neutrons or protons.
In 1934, an experiment showed that when natural Bi is bombarded with neutrons, Bi is created, which then decays to Po via beta-minus decay. By irradiating certain bismuth salts containing light element nuclei such as beryllium, a cascading (α,n) reaction can also be induced to produce Po in large quantities. The final purification is done pyrochemically followed by liquid-liquid extraction techniques. Polonium may now be made in milligram amounts in this procedure which uses high neutron fluxes found in nuclear reactors. Only about 100 grams are produced each year, practically all of it in Russia, making polonium exceedingly rare.
This process can cause problems in lead-bismuth based liquid metal cooled nuclear reactors such as those used in the Soviet Navy's K-27. Measures must be taken in these reactors to deal with the unwanted possibility of Po being released from the coolant.
The longer-lived isotopes of polonium, Po and Po, can be formed by proton or deuteron bombardment of bismuth using a cyclotron. Other more neutron-deficient and more unstable isotopes can be formed by the irradiation of platinum with carbon nuclei.
Applications
Polonium-based sources of alpha particles were produced in the former Soviet Union. Such sources were applied for measuring the thickness of industrial coatings via attenuation of alpha radiation.
Because of intense alpha radiation, a one-gram sample of Po will spontaneously heat up to above 500 °C (932 °F) generating about 140 watts of power. Therefore, Po is used as an atomic heat source to power radioisotope thermoelectric generators via thermoelectric materials. For example, Po heat sources were used in the Lunokhod 1 (1970) and Lunokhod 2 (1973) Moon rovers to keep their internal components warm during the lunar nights, as well as the Kosmos 84 and 90 satellites (1965).
The alpha particles emitted by polonium can be converted to neutrons using beryllium oxide, at a rate of 93 neutrons per million alpha particles. Po-BeO mixtures are used as passive neutron sources with a gamma-ray-to-neutron production ratio of 1.13 ± 0.05, lower than for nuclear fission-based neutron sources. Examples of Po-BeO mixtures or alloys used as neutron sources are a neutron trigger or initiator for nuclear weapons and for inspections of oil wells. About 1500 sources of this type, with an individual activity of 1,850 Ci (68 TBq), had been used annually in the Soviet Union.
Polonium was also part of brushes or more complex tools that eliminate static charges in photographic plates, textile mills, paper rolls, sheet plastics, and on substrates (such as automotive) prior to the application of coatings. Alpha particles emitted by polonium ionize air molecules that neutralize charges on the nearby surfaces. Some anti-static brushes contain up to 500 microcuries (20 MBq) of Po as a source of charged particles for neutralizing static electricity. In the US, devices with no more than 500 μCi (19 MBq) of (sealed) Po per unit can be bought in any amount under a "general license", which means that a buyer need not be registered by any authorities. Polonium needs to be replaced in these devices nearly every year because of its short half-life; it is also highly radioactive and therefore has been mostly replaced by less dangerous beta particle sources.
Tiny amounts of Po are sometimes used in the laboratory and for teaching purposes—typically of the order of 4–40 kBq (0.11–1.08 μCi), in the form of sealed sources, with the polonium deposited on a substrate or in a resin or polymer matrix—are often exempt from licensing by the NRC and similar authorities as they are not considered hazardous. Small amounts of Po are manufactured for sale to the public in the United States as "needle sources" for laboratory experimentation, and they are retailed by scientific supply companies. The polonium is a layer of plating which in turn is plated with a material such as gold, which allows the alpha radiation (used in experiments such as cloud chambers) to pass while preventing the polonium from being released and presenting a toxic hazard.
Polonium spark plugs were marketed by Firestone from 1940 to 1953. While the amount of radiation from the plugs was minuscule and not a threat to the consumer, the benefits of such plugs quickly diminished after approximately a month because of polonium's short half-life and because buildup on the conductors would block the radiation that improved engine performance. (The premise behind the polonium spark plug, as well as Alfred Matthew Hubbard's prototype radium plug that preceded it, was that the radiation would improve ionization of the fuel in the cylinder and thus allow the motor to fire more quickly and efficiently.)
Biology and toxicity
Overview
Polonium can be hazardous and has no biological role. By mass, polonium-210 is around 250,000 times more toxic than hydrogen cyanide (the LD50 for Po is less than 1 microgram for an average adult (see below) compared with about 250 milligrams for hydrogen cyanide). The main hazard is its intense radioactivity (as an alpha emitter), which makes it difficult to handle safely. Even in microgram amounts, handling Po is extremely dangerous, requiring specialized equipment (a negative pressure alpha glove box equipped with high-performance filters), adequate monitoring, and strict handling procedures to avoid any contamination. Alpha particles emitted by polonium will damage organic tissue easily if polonium is ingested, inhaled, or absorbed, although they do not penetrate the epidermis and hence are not hazardous as long as the alpha particles remain outside the body and do not come near the eyes, which are living tissue. Wearing chemically resistant and intact gloves is a mandatory precaution to avoid transcutaneous diffusion of polonium directly through the skin. Polonium delivered in concentrated nitric acid can easily diffuse through inadequate gloves (e.g., latex gloves) or the acid may damage the gloves.
Polonium does not have toxic chemical properties.
It has been reported that some microbes can methylate polonium by the action of methylcobalamin. This is similar to the way in which mercury, selenium, and tellurium are methylated in living things to create organometallic compounds. Studies investigating the metabolism of polonium-210 in rats have shown that only 0.002 to 0.009% of polonium-210 ingested is excreted as volatile polonium-210.
Acute effects
The median lethal dose (LD50) for acute radiation exposure is about 4.5 Sv. The committed effective dose equivalent Po is 0.51 μSv/Bq if ingested, and 2.5 μSv/Bq if inhaled. A fatal 4.5 Sv dose can be caused by ingesting 8.8 MBq (240 μCi), about 50 nanograms (ng), or inhaling 1.8 MBq (49 μCi), about 10 ng. One gram of Po could thus in theory poison 20 million people, of whom 10 million would die. The actual toxicity of Po is lower than these estimates because radiation exposure that is spread out over several weeks (the biological half-life of polonium in humans is 30 to 50 days) is somewhat less damaging than an instantaneous dose. It has been estimated that a median lethal dose of Po is 15 megabecquerels (0.41 mCi), or 0.089 micrograms (μg), still an extremely small amount. For comparison, one grain of table salt is about 0.06 mg = 60 μg.
Long term (chronic) effects
In addition to the acute effects, radiation exposure (both internal and external) carries a long-term risk of death from cancer of 5–10% per Sv. The general population is exposed to small amounts of polonium as a radon daughter in indoor air; the isotopes Po and Po are thought to cause the majority of the estimated 15,000–22,000 lung cancer deaths in the US every year that have been attributed to indoor radon. Tobacco smoking causes additional exposure to polonium.
Regulatory exposure limits and handling
The maximum allowable body burden for ingested Po is only 1.1 kBq (30 nCi), which is equivalent to a particle massing only 6.8 picograms. The maximum permissible workplace concentration of airborne Po is about 10 Bq/m (3×10 μCi/cm). The target organs for polonium in humans are the spleen and liver. As the spleen (150 g) and the liver (1.3 to 3 kg) are much smaller than the rest of the body, if the polonium is concentrated in these vital organs, it is a greater threat to life than the dose which would be suffered (on average) by the whole body if it were spread evenly throughout the body, in the same way as caesium or tritium (as T2O).
Po is widely used in industry, and readily available with little regulation or restriction. In the US, a tracking system run by the Nuclear Regulatory Commission was implemented in 2007 to register purchases of more than 16 curies (590 GBq) of polonium-210 (enough to make up 5,000 lethal doses). The IAEA "is said to be considering tighter regulations ... There is talk that it might tighten the polonium reporting requirement by a factor of 10, to 1.6 curies (59 GBq)." As of 2013, this is still the only alpha emitting byproduct material available, as a NRC Exempt Quantity, which may be held without a radioactive material license.
Polonium and its compounds must be handled with caution inside special alpha glove boxes, equipped with HEPA filters and continuously maintained under depression to prevent the radioactive materials from leaking out. Gloves made of natural rubber (latex) do not properly withstand chemical attacks, a.o. by concentrated nitric acid (e.g., 6 M HNO3) commonly used to keep polonium in solution while minimizing its sorption onto glass. They do not provide sufficient protection against the contamination from polonium (diffusion of Po solution through the intact latex membrane, or worse, direct contact through tiny holes and cracks produced when the latex begins to suffer degradation by acids or UV from ambient light); additional surgical gloves are necessary (inside the glovebox to protect the main gloves when handling strong acids and bases, and also from outside to protect the operator hands against Po contamination from diffusion, or direct contact through glove defects). Chemically more resistant, and also denser, neoprene and butyl gloves shield alpha particles emitted by polonium better than natural rubber. The use of natural rubber gloves is not recommended for handling Po solutions.
Cases of poisoning
Despite the element's highly hazardous properties, circumstances in which polonium poisoning can occur are rare. Its extreme scarcity in nature, the short half-lives of all its isotopes, the specialised facilities and equipment needed to obtain any significant quantity, and safety precautions against laboratory accidents all make harmful exposure events unlikely. As such, only a handful of cases of radiation poisoning specifically attributable to polonium exposure have been confirmed.
20th century
In response to concerns about the risks of occupational polonium exposure, quantities of Po were administered to five human volunteers at the University of Rochester from 1944 to 1947, in order to study its biological behaviour. These studies were funded by the Manhattan Project and the AEC. Four men and a woman participated, all suffering from terminal cancers, and ranged in age from their early thirties to early forties; all were chosen because experimenters wanted subjects who had not been exposed to polonium either through work or accident. Po was injected into four hospitalised patients, and orally given to a fifth. None of the administered doses (all ranging from 0.17 to 0.30 μCi kg) approached fatal quantities.
The first documented death directly resulting from polonium poisoning occurred in the Soviet Union, on 10 July 1954. An unidentified 41-year-old man presented for medical treatment on 29 June, with severe vomiting and fever; the previous day, he had been working for five hours in an area in which, unknown to him, a capsule containing Po had depressurised and begun to disperse in aerosol form. Over this period, his total intake of airborne Po was estimated at 0.11 GBq (almost 25 times the estimated LD50 by inhalation of 4.5 MBq). Despite treatment, his condition continued to worsen and he died 13 days after the exposure event.
From 1955 to 1957 the Windscale Piles had been releasing polonium-210. The Windscale fire brought the need for testing of the land downwind for radioactive material contamination, and this is how it was found. An estimate of 8.8 terabecquerels (240 Ci) of polonium-210 has been made.
It has also been suggested that Irène Joliot-Curie's 1956 death from leukaemia was owed to the radiation effects of polonium. She was accidentally exposed in 1946 when a sealed capsule of the element exploded on her laboratory bench.
As well, several deaths in Israel during 1957–1969 have been alleged to have resulted from Po exposure. A leak was discovered at a Weizmann Institute laboratory in 1957. Traces of Po were found on the hands of Professor Dror Sadeh, a physicist who researched radioactive materials. Medical tests indicated no harm, but the tests did not include bone marrow. Sadeh, one of his students, and two colleagues died from various cancers over the subsequent few years. The issue was investigated secretly, but there was never any formal admission of a connection between the leak and the deaths.
The Church Rock uranium mill spill July 16, 1979 is reported to have released polonium-210. The report states animals had higher concentrations of lead-210, polonium-210 and radium-226 than the tissues from control animals.
21st century
Further information: Poisoning of Alexander Litvinenko and Cause of Yasser Arafat's deathThe cause of the 2006 death of Alexander Litvinenko, a former Russian FSB agent who had defected to the United Kingdom in 2001, was identified to be poisoning with a lethal dose of Po; it was subsequently determined that the Po had probably been deliberately administered to him by two Russian ex-security agents, Andrey Lugovoy and Dmitry Kovtun. As such, Litvinenko's death was the first (and, to date, only) confirmed instance in which polonium's extreme toxicity has been used with malicious intent.
In 2011, an allegation surfaced that the death of Palestinian leader Yasser Arafat, who died on 11 November 2004 of uncertain causes, also resulted from deliberate polonium poisoning, and in July 2012, concentrations of Po many times more than normal were detected in Arafat's clothes and personal belongings by the Institut de Radiophysique in Lausanne, Switzerland. Even though Arafat's symptoms were acute gastroenteritis with diarrhoea and vomiting, the institute's spokesman said that despite the tests the symptoms described in Arafat's medical reports were not consistent with Po poisoning, and conclusions could not be drawn. In 2013 the team found levels of polonium in Arafat's ribs and pelvis 18 to 36 times the average, even though by this point in time the amount had diminished by a factor of 2 million. Forensic scientist Dave Barclay stated, "In my opinion, it is absolutely certain that the cause of his illness was polonium poisoning. ... What we have got is the smoking gun - the thing that caused his illness and was given to him with malice." Subsequently, French and Russian teams claimed that the elevated Po levels were not the result of deliberate poisoning, and did not cause Arafat's death.
It has also been suspected that Russian businessman Roman Tsepov was killed with polonium. He had symptoms similar to Aleksander Litvinenko.
Treatment
It has been suggested that chelation agents, such as British anti-Lewisite (dimercaprol), can be used to decontaminate humans. In one experiment, rats were given a fatal dose of 1.45 MBq/kg (8.7 ng/kg) of Po; all untreated rats were dead after 44 days, but 90% of the rats treated with the chelation agent HOEtTTC remained alive for five months.
Detection in biological specimens
Polonium-210 may be quantified in biological specimens by alpha particle spectrometry to confirm a diagnosis of poisoning in hospitalized patients or to provide evidence in a medicolegal death investigation. The baseline urinary excretion of polonium-210 in healthy persons due to routine exposure to environmental sources is normally in a range of 5–15 mBq/day. Levels in excess of 30 mBq/day are suggestive of excessive exposure to the radionuclide.
Occurrence in humans and the biosphere
Polonium-210 is widespread in the biosphere, including in human tissues, because of its position in the uranium-238 decay chain. Natural uranium-238 in the Earth's crust decays through a series of solid radioactive intermediates including radium-226 to the radioactive noble gas radon-222, some of which, during its 3.8-day half-life, diffuses into the atmosphere. There it decays through several more steps to polonium-210, much of which, during its 138-day half-life, is washed back down to the Earth's surface, thus entering the biosphere, before finally decaying to stable lead-206.
As early as the 1920s, French biologist Antoine Lacassagne, using polonium provided by his colleague Marie Curie, showed that the element has a specific pattern of uptake in rabbit tissues, with high concentrations, particularly in liver, kidney, and testes. More recent evidence suggests that this behavior results from polonium substituting for its congener sulfur, also in group 16 of the periodic table, in sulfur-containing amino-acids or related molecules and that similar patterns of distribution occur in human tissues. Polonium is indeed an element naturally present in all humans, contributing appreciably to natural background dose, with wide geographical and cultural variations, and particularly high levels in arctic residents, for example.
Tobacco
Polonium-210 in tobacco contributes to many of the cases of lung cancer worldwide. Most of this polonium is derived from lead-210 deposited on tobacco leaves from the atmosphere; the lead-210 is a product of radon-222 gas, much of which appears to originate from the decay of radium-226 from fertilizers applied to the tobacco soils.
The presence of polonium in tobacco smoke has been known since the early 1960s. Some of the world's biggest tobacco firms researched ways to remove the substance—to no avail—over a 40-year period. The results were never published.
Food
Polonium is found in the food chain, especially in seafood.
See also
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External links
- Polonium at The Periodic Table of Videos (University of Nottingham)
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