What is radioactive decay?

Some isotopes of certain elements have an atomic structure that is naturally unstable. This is where the nucleus of an atom is unstable because it has the wrong number of neutrons relative to its number of protons. Radioactive decay is the way that these unstable atoms emit or radiate excess energy in the form of particles or waves. Depending on how the nucleus loses this excess energy, it may form a lower energy isotope of the same element. Or it could lose enough particles to become a different element altogether.

Video segment. Assistance may be required. This lesson will explore three different types of radiation or radioactive decay. First, as an introduction to the topic, watch the following video.

Source, Ionizing Radiation "What is ionizing radiation" P1, KSU Information, Youtube