po·lo·ni·um   (pə-lō'nē-əm)    n.   Symbol Po A naturally radioactive metallic element, occurring in minute quantities as a product of radium disintegration and produced by bombarding bismuth or lead with neutrons. It has 27 isotopes ranging in mass number from 192 to 218, of which Po 210, with a half-life of 138.39 days, is the most readily available. Atomic number 84; melting point 254°C; boiling point 962°C; specific gravity 9.32; valence 2, 4. See Table at element. [From Medieval Latin Polōnia, Poland (the native country of Pierre and Marie Curie, the element's discoverers).]

Main Entry: po·lo·ni·um
Pronunciation: p&-'lO-nE-&m
Function: noun
: a radioactive metallic element that is similar chemicallyto tellurium and bismuth, occurs especially in pitchblende and radium-lead residues, and emits an alpha particle to form an isotope of lead —symbol Po; —see ELEMENT table

polonium po·lo·ni·um (pə-lō'nē-əm)
n.
Symbol Po
A naturally radioactive metallic element, occurring in minute quantities in uranium ores; its most readily available isotope is Po 210, with a half-life of 138.39 days. Atomic number 84; melting point 254°C; boiling point 962°C; specific gravity 9.32; valence 2, 4.

polonium

a radioactive, silvery-gray or black metallic element of the oxygen family (Group VIa in the periodic table). The first element to be discovered by radiochemical analysis, polonium was discovered in 1898 by Pierre and Marie Curie, who were investigating the radioactivity of a certain pitchblende, a uranium ore. Polonium is a very rare element (its abundance in the Earth's crust is about one part in 1015) that 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.

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