The mineral that is highly reactive and used as a source of atomic energy for both bombs and nuclear-powered generating plants is Uranium. Uranium is a radioactive element with the atomic number 92. It is the heaviest naturally occurring element and is found in small amounts in many rocks and soils. When Uranium-235, a particular isotope of Uranium, is bombarded with neutrons, it undergoes nuclear fission, releasing large amounts of energy in the form of heat and radiation. This process is what powers nuclear reactors and atomic bombs.