If the binding energy is very strong then the proton or neutron cannot be emitted and we ave a stable nucleus. Radioactivity is inside the nucleus and cannot be influenced from the outside, such as temperature or pressure. Half-life is defined as the time it takes for half the nucleons to emit either a proton or neutron. This half-life of radioactive elements can be used to determine how old a sample is by measuring the ratio of the unchanged atoms to the changed ones. Radiation can be dangerous to humans or other animals, as the emitted proton or neutron can damage material along its path, by changing the nucleus, and thereby changing the atom.
Nuclear reactions can change one nucleus into another nucleus.
Besides protons and neutron we can have electrons emitted by radioactive nucleus called beta rays . Anytime we can change an element from one nucleus to another and the binding energy is reduced, energy is emitted. If this energy can be harness, we have nuclear energy. If the nucleus breaks up into lighter elements, it is called fission . If several nuclei are combined together to form a more massive nucleus, the process is called nuclear fusion .