What are examples of nuclear changes in mass?

Answer 1

Changes in nuclear mass can happen when, say, radioactive decay occurs and a nucleus loses mass. When an unstable atomic nucleus "adjusts" to a new state, it dumps a particle or particles, and energy, and its mass decreases. Certainly nuclear fission will cause a dramatic reduction in nuclear mass, but this is the actual "breaking up" of a nucleus into smaller nuclei called fission fragments. Perhaps an example will help. The element radon is an inert gas, but it has no stable isotopes. It's most stable isotope, 222Rn, appears as a decay product of radium; it's a radioactive daughter. It turns out that 222Rn decays by alpha emission, and that means that two neutrons and two protons are kicked out of the nucleus. This will produce the radioactive daughter product polonium-218. It is possible for a nucleus to absorb a particle and gain mass. Frequently this will cause nuclear instability (if it doesn't actually initiate fission) and create a radionuclide, which is unstable and will eventually decay. But something like, say, neutron absorption (neutron capture) will result in an atomic nuclei with a greater mass than the original atomic nucleus that absorbed that neutron. It is of note that fusion knits smaller nuclei or particles together to create a larger nucleus, but this may not necessarily be considered a "simple increase" of mass in a nucleus, though the resultant nucleus will be heavier than any constituent nucuei or particles. You may want an example. If we stick some uranium-238 into an operating nuclear reactor, the 238U will absorb a neutron to become 239U, which is heavier by one neutron that the atomic nucleus that absorbed that neutron. (The 239U is unstable and decays in a couple of steps to make 239Pu, which is used as the fissile material in most nuclear bombs and as a fuel in some nuclear reactors.) Use the links below to related articles posted by our friends at Wikipedia, where knowledge is free.