Name Plutonium
Symbol Pu
Atomic Number 94
Atomic Mass 244 atomic mass units
Number of Protons 94
Number of Neutrons 150
Number of Electrons 94
Melting Point 639.5 C
Boiling Point 3235.0 C
Density 2.62 grams per cubic centimeter
Normal Phase Synthetic
Family Rare Earth Metals
Period 7
Cost Unknown



Origin of Name After Pluto, which was once a planet
Date of Discovery In 1940 at the Los Alamos National Laboratory in California
Discovered by Glenn Theodore Seaborg, Joseph W. Kennedy, Edward M. McMillan and Arthur C. Wohl
Common Compounds
Interesting facts
  • It is found in uranium ores.
  • It has been called the most complex metal and a physicist's dream but an engineer's nightmare.
  • It is very sensitive to changes in temperature, pressure, or chemistry.
  • It is usually alloyed with small amounts of gallium.
  • Seaborg chose "Pu" for the symbol as a joke and it appeared on the periodic table without any questioning.
  • They thought about naming it ultinium or extremium, because they thought they had found the last element.
  • While working on the Manhattan Project, scientists studied the effects of plutonium on laboratory animals and human subjects
Common Uses


Photo Courtesy of
Chemical Elements
Jefferson Labs

Plutonium Atomic Structure Elements by Name Elements by Number Home