Plutonium is one of the several radioactive elements on the periodic table.It is in the actinides group, and was named after Pluto. Being radioactive means that the element is so unstable, that it is constantly emitting, or radiating harmful particles. Plutonium was discovered by Glenn T. Seaborg and his colleagues in 1941.
The half life of an element is the amount of time it takes for the atomic number and mass of the element to reach half of it's original number and mass. Plutonium-239 has a half life of 24,200 years.


Plutonium has an atomic number of 94, this means it has 94 protons, and electrons. It has an atomic mass of 244, however, there are many isotopes of Plutonium, with atomic masses ranging from 232 to 246.
Plutonium is a transuranic element. These are elements with atomic numbers higher than 92. Transuranic elements do not occur in nature. However, traces of plutonium are sometimes found in nature, however, the majority of it is created in nuclear reactors as a byproduct of uranium.
Plutonium has been used in both nuclear reactors and nuclear bombs. However, since it is slightly more unstable than uranium, it is more often used in nuclear bombs.
The isotope of plutonium with the lowest critical mass is plutonium-238 (9.04–10.07kg). Critical mass is the least amount of a fissile material necessary for it to begin a sustained nuclear chain reaction. What this means, is that if a chain reaction was started with at least 9.04kg of plutonium-238, it would be self sustaining. Any less mass, and the reaction would stop if not manually sustained.
Melting Point: 641 deg. C
Boiling Point: 3232 deg. C
Density: 16 to 20 grams per cubic centimeter

Weapons Grade Plutonium

The most common isotope of plutonium, which is also the isotope most useful for making nuclear weapons is plutonium-239. This isotope is only produced when uranium-238 absorbs a neutron and then rapidly decays into plutonium-239. There is not enough naturally occurring Pu-239 in the world to create a major weapons supply. This plutonium isotope is produced in almost all nuclear reactors. There are some nuclear reactor that are used specifically for creating weapons grade plutonium. Most isotopes of plutonium can be used in nuclear weapons. The only grade of plutonium which could not be used for weapons is pure plutonium-238. It would generate too much heat, thus making the weapon unstable. The atomic bomb that was dropped on Nagasaki, "Fat Man" was an implosion type bomb with a plutonium core. The explosive power of an atomic bomb is measured in yield, which is expressed as tons of TNT.
An atomic bomb.
Mockup of "Fat Man"

Nuclear Reaction

Nuclear reactions are unlike chemical reactions, in the sense that there is only one element involved. In a nuclear reaction, neutrons are fired at the radioactive material, the atoms of the material are so unstable, that they split in two when they are hit with neutrons. This splitting releases more neutrons, and a lot of energy. If you have critical mass, then the reaction would sustain itself until there is not enough material. In nuclear reactors, this reaction occurs slowly, and the heat is used to power steam turbines. In a nuclear bomb, the reaction occurs instantly, releasing all the energy at once. This is called an explosion.

Radioactive Symbol_RGB.jpg
This is the radioactive symbol.

Dirty Bombs

Dirty bombs are non-nuclear devices that contain nuclear material such as plutonium or uranium. The point of a dirty bomb is not to cause physical damage to an area, but to make the area impossible to inhabit because of radiation. These devices use normal explosives with radioactive materials in the device, there is no nuclear reaction, but the radiation is extremely toxic. Dirty bombs also cause major panic and psychological problems.

Miscellaneous Info and Fascinating Facts

Plutonium is a silvery white color. When someone says that Plutonium is reactive, they do not mean chemically reactive, they mean that it is radioactive. However, plutonium does react to air which oxidizes it and turns it into a grayish color. Plutonium oxide would also be the only compound containing plutonium, however, it is not common.
These are some fascinating facts:
  • "Fat Man" was one of the only two nuclear weapons actually used in war.
  • Pellets of Plutonium less than 1 millimeter diameter would spontaneously ignite at 150 deg. C
  • Alfie Maddock, a nuclear scientist, was working with the U.K.'s entire supply of plutonium, (about 10 mg) when he spilled it on the lab table. To get it back, he sawed off a chunk of the table, and burned it. He got back 9.5 mg of it, and no one would have known, but he was too tired to repair the table.