polonium (puh-LOH-nee-uhm) 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.It comes from Medieval Latin Polnia, Poland, the native country of Pierre and Marie Curie, the element's discoverers.
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