uranium -- splits into fragments of smaller total mass. The mass difference between the original element and its split constituents is released as energy. This phenomenon underpins all research into nuclear energy, which is an alternative to the energy generated...
You’ve probably heard of uranium-235 and, well, the polonium-210 that did in former KGB officer Alexander Litvinenko. The former is moderately radioactive, the latter horrendously so. But there are all sorts of stable6 isotopes, too. For example, silver comes in two of them, 107 and ...