Absolute dating via RADIOMETRIC DATING depends on our finding elements that decay radioactively into other elements at a known rate-uranium into lead, for example, or potassium into argon. By measuring and comparing the amounts of the original element and its decay product in a rock sample, a scientist may be able to calculate how long ago the rock formed.
Matter and Minerals -- Radioactivity: Expect the unexpected -- Ted Ed Talk
Neutrons don’t change into protons. Except, sometimes, they do. Radioactivity is the process under which the nucleus can change spontaneously from one element to another. Steve Weatherell suggests that we acknowledge both the usefulness and danger inherent in harvesting radioactivity.