Nuclear Bomb
An atomic bomb is an extremely powerful explosive weapon whose power is fuelled by the splitting (fission) of the nuclei of isotopes of uranium or plutonium (uranium-235, uranium-238, and plutonium-239) in a chain reaction. When such atoms are split very large amounts of energy are released. This power can also come from, fusion where hydrogen isotopes of deuterium and tritium are forced together by using a fission reaction. When such atoms are fused together the resulting helium atoms have a slightly smaller mass than the hydrogen isotopes from which they were formed. There remainder of mass must go somewhere so it becomes vast amounts of energy. This bomb is called a hydrogen bomb and is more powerful than a fission bomb. Since the hydrogen bomb needs a fission bomb in order to function, it was naturally invented after the fission bomb. Nowadays most of the existing nuclear arsenals are composed mainly of hydrogen bombs. Since the manufacture of these weapons is so difficult and expensive only a few nations in the world have them. Terrorists so far are not know to have ever manufactured or to posses nuclear weapons.