polonium
/peuh loh"nee euhm/, n. Chem.
a radioactive element discovered by Pierre and Marie Curie in 1898; Symbol: Po; at. no.: 84; at. wt.: about 210.
[1895-1900; < NL, equiv. to polon- ( < ML Polonia Poland) + -ium -IUM]

* * *

 a radioactive, silvery-gray or black metallic element of the oxygen group (oxygen group element) (Group 16 [VIa] in the periodic table). The first element to be discovered by radiochemical analysis, polonium was discovered in 1898 by Pierre (Curie, Pierre) and Marie Curie (Curie, Marie), who were investigating the radioactivity of a certain pitchblende, a uranium ore. The very intense radioactivity not attributable to uranium was ascribed to a new element, named by them after Marie Curie's homeland, Poland. The discovery was announced in July 1898. Polonium is extremely rare, even in pitchblende: 1,000 tons of the ore must be processed to obtain 40 milligrams of polonium. Its abundance in the Earth's crust is about one part in 1015. It occurs in nature as a radioactive decay product of uranium, thorium, and actinium. The half-lives of its isotopes range from a fraction of a second up to 103 years; the most common natural isotope of polonium, polonium-210, has a half-life of 138.4 days.

      Polonium usually is isolated from by-products of the extraction of radium from uranium minerals. In the chemical isolation, pitchblende ore is treated with hydrochloric acid, and the resulting solution is heated with hydrogen sulfide to precipitate polonium monosulfide, PoS, along with other metal sulfides, such as that of bismuth, Bi2S3, which resembles polonium monosulfide closely in chemical behaviour, though it is less soluble. Because of the difference in solubility, repeated partial precipitation of the mixture of sulfides concentrates the polonium in the more soluble fraction, while the bismuth accumulates in the less soluble portions. The difference in solubility is small, however, and the process must be repeated many times to achieve a complete separation. Purification is accomplished by electrolytic deposition. It can be produced artificially by bombarding bismuth or lead with neutrons or with accelerated charged particles.

      Chemically, polonium resembles the elements tellurium and bismuth. Two modifications of polonium are known, an α- and a β-form, both of which are stable at room temperature and possess metallic characteristics. The fact that its electrical conductivity decreases as the temperature increases places polonium among the metals rather than the metalloids or nonmetals.

      Because polonium is highly radioactive—it disintegrates to a stable isotope of lead by emitting alpha rays, which are streams of positively charged particles—it must be handled with extreme care. When contained in such substances as gold foil, which prevent the alpha radiation from escaping, polonium is used industrially to eliminate static electricity generated by such processes as paper rolling, the manufacture of sheet plastics, and the spinning of synthetic fibres. It is also used on brushes for removing dust from photographic film and in nuclear physics as a source of alpha radiation. Mixtures of polonium with beryllium or other light elements are used as sources of neutrons.

atomic number
84
atomic weight
210
melting point
254 °C (489 °F)
boiling point
962 °C (1,764 °F)
density
9.4 g/cm3
oxidation states
−2, +2, +3(?), +4, +6
electronic config.
1s22s22p63s23p63d104s24p64d104f145s25p65d106s26p4
Robert C. Brasted
 

* * *


Universalium. 2010.

Look at other dictionaries:

  • Polonium — (] [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]… …   Wikipedia

  • POLONIUM — Le polonium (symbole Po, numéro atomique 84) est un élément radioactif découvert par Pierre et Marie Curie, en 1898, dans la pechblende de Joachimsthal. Ayant observé que la radioactivité des minerais d’uranium était supérieure à celle que l’on… …   Encyclopédie Universelle

  • Polonium — Bismuth ← Polonium → Astate Te …   Wikipédia en Français

  • Polonium — Po*lo ni*um (p[ o]*l[=o] n[i^]*[u^]m), n. [NL. So named after Poland, in L. form Polonia, one of the discoverers being a Pole.] (Chem.) A radioactive chemical element, discovered by M. and MMe. Curie in pitchblende, and originally called {radium… …   The Collaborative International Dictionary of English

  • Polonĭum — Polonĭum, ein in Pechblende enthaltenes Metall, das aus Wismutpoloniumlösung durch Eintauchen von Wismut als äußerst aktive Schicht (4 mg aus 2000 kg Pechblende) erhalten wird; es ist ähnlich dem Wismut. Vgl. Radioaktivität …   Meyers Großes Konversations-Lexikon

  • Polonium — Polonĭum, vom Ehepaar Curie 1898 im Uranpecherz aufgefundenes, stark radioaktives chem. Element. Seine Existenz ist neuerdings wieder zweifelhaft geworden …   Kleines Konversations-Lexikon

  • polonium — POLÓNIUM s.n. v. poloniu. Trimis de LauraGellner, 13.09.2007. Sursa: DN …   Dicționar Român

  • polonium — Symbol: Po Atomic number: 84 Atomic weight: (210) Rare radioactive metallic element, belongs to group 16 of the periodic table. Over 30 known isotopes exist, the most of all elements. Po 209 has a half life of 103 years. Possible uses in heating… …   Elements of periodic system

  • polonium — radioactive element, discovered 1898 by Marie Curie and her husband and named for her native country, POLAND (Cf. Poland) (Modern Latin Polonia) …   Etymology dictionary

  • polonium — [pə lō′nē əm] n. [ModL: so named (1898) by its co discoverer CURIE Marie, after her native land, Poland (ML Polonia) + IUM] a radioactive, nonmetallic chemical element formed naturally by the disintegration of radium or synthetically by the… …   English World dictionary

  • Polonium — Eigenschaften …   Deutsch Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”