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 po·lo·ni·um /pəˈloniəm/
 釙

 po·lo·ni·um /pəˈlonɪəm/ 名詞
 釙

 Po·lo·ni·um n.  Chem. A radioactive chemical element, discovered by M. and MMe. Curie in pitchblende, and originally called radium F.  It has atomic number 84 and an atomic weight of 210.  It is a very rare natural element, having an abundance in uranium ores only 0.2% that of radium.  It is closely related chemically to bismuth. It emits only alpha rays, and has a half-life of 138 days.  It is thus more unstable than radium, and a milligram of polonium emits as many alpha particles as 5 grams of radium.  Twenty-seven isotopes are known, with atomic masses from 192 to 218. At present a more practical method of preparation than isolation from ores is the preparation by neutron bombardment of bismuth in a nuclear reactor, and it may be obtained commercially by users having an appropriate permit. --[HBCF61]
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 polonium
      n : a radioactive metallic element that is similar to tellurium
          and bismuth; occurs in uranium ores but can be produced
          by bombarding bismuth with neutrons in a nuclear reactor
          [syn: Po, atomic number 84]

 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 spacecraft. Discovered
 by Marie Curie in 1898 in a sample of pitchblende.