Plutonium (Pu)

Isotopes of Plutonium 

Isotope Atomic Mass Half-life Mode of Decay Nuclear Spin Nuclear Magnetic Moment
Pu-236 236.04605 2.87 years α to U-232;
 0 No data available 
Pu-237 237.04840 45.70 days EC to Np-237;
α to U-232
 7/2 No data available 
Pu-238 238.04955 87.74 years α to U-234;
 0 No data available 
Pu-239 239.05216 24,110 years α to U-235;
 1/2 0.203
Pu-240 240.05381 6537 years α to U-236;
 0 No data available 
Pu-241 241.05684 14.40 years α to U-237; SF;
ß- to Am-241
 5/2 -0.683
Pu-242 242.05874 3.76 x 105 years α to U-238; SF  0 No data available 
Pu-243 243.06200 4.956 hours ß- to Am-243  7/2 No data available 
Pu-244 244.064199 8.20 x 107 years α to U-240; SF  0 No data available 
Pu-245 245.06774 10.50 hours ß- to Am-245  9/2 No data available 
Pu-246 246.07020 10.85 days ß- to Am-246  0 No data available 


Plutonium, named for the planet Pluto, is the second transuranium element of the actinide series to have been discovered. It was synthesized in 1940 by Glenn T. Seaborg, Joseph William Kennedy, Edward M. McMillan and Arthur C. Wahl in a cyclotron in Berkeley, California, USA.

Plutonium, like most metals, has a bright silvery appearance at first, much like nickel, but it oxidizes very quickly to a dull gray, although yellow and olive green are also reported. At room temperature plutonium is in its α form (alpha). This, the most common allotrope of the element, is about as hard and brittle as grey cast iron unless it is alloyed with other metals to make it soft and ductile. Unlike most metals, plutonium is not a good conductor of heat or electricity. It is a reactive metal. In moist air or moist argon, it oxidizes rapidly, producing a mixture of oxides and hydrides. Plutonium can also form alloys and intermediate compounds with most other metals.

Twenty radioactive isotopes of plutonium have been characterized. The longest-lived are Plutonium-244, with a half-life of about 80.8 million years; Plutonium-242, with a half-life of about 373,300 years; and Plutonium-239, with a half-life of 24,110 years. All of the remaining radioactive isotopes have half-lives that are less than 7,000 years. Of great importance is Plutonium-239, one kilogram of which provides the equivalent of nearly 22 million kilowatt hours of heat energy. The complete detonation of a kilogram of plutonium produces an explosion equal to that of about 20,000 tons of chemical explosive.

Practical applications of plutonium include nuclear weaponry, electrical power generation, spacecraft power sources, artificial heart pacemakers and scientific research.

Isotopes and compounds of plutonium are radioactive and accumulate in bone marrow. Acute or longer-term exposure can carry a danger of serious health outcomes including radiation sickness, genetic damage, cancer and death. The danger increases with the amount of exposure.

Properties of Plutonium

Name Plutonium
Symbol Pu
Atomic number 94
Atomic weight [244]
Standard state Solid at 298 °K
CAS Registry ID 7440-07-5
Group in periodic table N/A 
Group name Actinoid
Period in periodic table 7 (Actinoid)
Block in periodic table f-block
Color Silvery white
Classification Metallic
Melting point 912.5 °K [or 639.4 °C or 1182.9 °F]
Boiling point 3503 °K [or 3230 °C or 5846 °F]
Density of solid 19.82 g/cm3
Electron configuration [Rn]5f67s2