ABSTRACT
Radioactivity is the physical phenomenon by which unstable atoms spontaneously change into other atoms and, in the process, emit radiation. The resulting atom can be stable (nonradioactive) or it may be subject to further change (radioactive). If the resulting atom is also unstable, it is termed the “progeny” of the original, “parent” atom. If a parent atom changes or “decays” to a radioactive progeny, a decay chain can occur with one or more radioactive progeny, resulting finally in a stable atom. One familiar decay chain 558involves uranium atoms decaying through several steps to thorium, radium, radon, and eventually to lead.
