What is radio active decay? Radioactive Decay: A stable nucleus of an element has the correct balance of protons and neutrons. Isotopes of an element which have too few or too many neutrons are usually unstable. Carbon-12 is stable but carbon-14 which has 2 extra neutrons is unstable. Nitrogen-14 is stable but its isotope, nitrogen-13 which has 1 neutron less is … [Read more...] about What are the different types of radioactive decay?