[ ploo-toh-nee-uhm ]

nounChemistry, Physics.
  1. a transuranic element with a fissile isotope of mass number 239 (plutonium 239 ) that can be produced from non-fissile uranium 238, as in a breeder reactor. Symbol: Pu; atomic number: 94.

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Origin of plutonium

1940–45; <Greek PloútōnPluto + -ium

Words Nearby plutonium Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024

How to use plutonium in a sentence

British Dictionary definitions for plutonium


/ (pluːˈtəʊnɪəm) /

  1. a highly toxic metallic transuranic element. It occurs in trace amounts in uranium ores and is produced in a nuclear reactor by neutron bombardment of uranium-238. The most stable and important isotope, plutonium-239, readily undergoes fission and is used as a reactor fuel in nuclear power stations and in nuclear weapons. Symbol: Pu; atomic no: 94; half-life of 239 Pu: 24 360 years; valency: 3, 4, 5, or 6; relative density (alpha modification): 19.84; melting pt: 640°C; boiling pt: 3230°C

Origin of plutonium

C20: named after the dwarf planet Pluto because Pluto lies beyond Neptune and plutonium was discovered soon after neptunium

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for plutonium


[ plōō-tōnē-əm ]

  1. 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 80 million years. Atomic number 94; melting point 640°C; boiling point 3,228°C; specific gravity 19.84; valence 3, 4, 5, 6. See Periodic Table.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for plutonium


[ (plooh-toh-nee-uhm) ]

A radioactive chemical element that is artificially derived from uranium.

Notes for plutonium

Plutonium is used in nuclear reactors.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.