All elements have a specific name, for example uranium, oxygen, iron. Atoms of a specific element have the same number of protons within the nucleus, for example uranium has 92 protons, oxygen has 8 and iron 26. Radionuclides are referred to by the number of protons AND neutrons in the nucleus, for example uranium-238 (92 protons + 146 neutrons) and uranium-235 (92 protons + 143 neutrons).