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The symbol for the element plutonium.
The symbol for plutonium.
A silvery, radioactive metallic element of the actinide series that has the highest atomic number of all naturally occurring elements. It is found in minute amounts in uranium ores and is produced artificially by bombarding uranium with neutrons. It is absorbed by bone marrow and is highly poisonous. Plutonium is used in nuclear weapons and as a fuel in nuclear reactors. Its longest-lived isotope is Pu 244 with a half-life of 76 million years. Atomic number 94; melting point 640°C; boiling point 3,232°C; specific gravity 19.84; valence 3, 4, 5, 6. See Periodic Table.
radioactive chemical element of the actinoid series of the periodic table, atomic number 94. It is the most important transuranium element because of its use as fuel in certain types of nuclear reactors and as an ingredient in nuclear weapons. Plutonium, warm because of energy released in alpha decay, is a silvery metal that takes on a yellow tarnish in air. The element was first detected (1941) as the isotope plutonium-238 by Glenn T. Seaborg, Joseph W. Kennedy, and Arthur C. Wahl, who produced it by deuteron bombardment of uranium-238 in the 60-inch cyclotron at Berkeley, California. Traces of plutonium have subsequently been found in uranium ores, where it is not primeval but naturally produced by neutron irradiation