Uranium-235
Uranium-235 is a radioactive isotope of uranium. Uranium-235 has 143 neutrons, 92 protons, and an isotope mass of 235.0439299.  Uranium-235 has 235Pa, 235Np, and 239Pu as its parent isotopes.  As it decays, it produces 231Th. Uranium-235 has a half-life of 703.8 million years. Uranium-235 makes up about 0.72% of natural uranium. When it is separated from the other uranium isotopes, it is called enriched uranium. The main use for enriched uranium is in Nuclear reactors.