Name       : Plutonium
Symbol     : Pu
Atomic #   : 94
Atom weight: 242 (Most stable isotope)
Melting P. : 641
Boiling P. : 3232
Oxidation  : +3, +4, +5, +6
Pronounced : ploo-TOE-ni-em
From       : Named for the planet Pluto
Identified : Glenn T. Seaborg in 1941
Appearance : Silvery-white, radioactive metal
Note       : Byproducts of atomic power plants
             Main ingredient in atomic fission weapons
             
[Properties]

  All isotopes of plutonium are radioactive. The half-lives range from about
26 minutes for plutonium-235 to 82-million years for plutonium-244. The most
widely produced isotopes, however are plutonium-238 and -239.
  There are six known allotropic, crystalline, metallic forms of plutonium.
The alpha version is the one that exists at normal environmental 
temperatures, so it is most widely recognized. The remaining allotropic form
exist at higher temperatures. A sample of alpha plutonium has a silvery 
color that takes on a yellowish hue as it oxidizes in the air.
  A softball-sized piece of plutonium would grow hot to the touch because of
its high level of alpha reaction. A somewhat larger sample can boil a litre
of water within a few minutes. A single kilogram of Pu-238 can release the
equivalent of 22-million kilowatt-hours of heat energy.
  Plutonium-238 is not fissionable; it cannot undergo a chain reaction.
Plutonium-239, on the other hand, is fissionable and can undergo a chain
reaction when compressed to its critical mass. In fact, the critical mass of
plutonium-239 is only about one-third that of fissionable uranium-235. A
kilogram of Pu-239 can release the explosive energy of 20,000 tons of TNT,
making it the material of choice for fission weaponry.