Nuclear Reactions - Nuclear Decay Chemical reactions all involve the exchange or sharing of electrons, they never have an influence on the nucleus of the atom.
Nuclear reactions involve a change in the nucleus.
Under certain arrangements of protons and neutrons the electrostatic force can cause instability in the nucleus causing it to decay. It will continue to decay until it reaches a stable combination. This graph shows the stable nuclei in red . The more protons in the nuclei, the more neutrons are needed for stability. Stability is favored by even numbers of protons and even numbers of neutrons.