Radioactive Decay

After reading this section you will be able to do the following:

  • Describe radioactive decay and transmutation.
  • Discuss the two forms of radiation that can be released due to radioactive decay.

What is radioactive decay?

Radioactive decay is the spontaneous breakdown of an atomic nucleus resulting in the release of energy and matter from the nucleus. Remember that a radioisotope has unstable nuclei that does not have enough binding energy to hold the nucleus together. Radioisotopes would like to be stable isotopes so they are constantly changing to try and stabilize. In the process, they will release energy and matter from their nucleus and often transform into a new element. This process, called transmutation, is the change of one element into another as a result of changes within the nucleus. The radioactive decay and transmutation process will continue until a new element is formed that has a stable nucleus and is not radioactive. Transmutation can occur naturally or by artificial means.

Two Principle Forms of Nuclear Radiation

The energy and matter released during radioactive decay is called nuclear radiation, and it takes on the following two principle forms:

  • The first type of nuclear radiation is known as particulate radiation. Particulate radiation consists of actual subatomic particles being emitted from the nucleus of the atom.
  • The second type is called electromagnetic radiation. Electromagnetic radiation, in simple terms, is energy in wave form that possesses both electrical and magnetic characteristics.

The two types of particulate radiation were a result of alpha and beta decay. Electromagnetic radiation is a result of gamma decay.


  1. As an unstable atom tries to reach a stable form, energy and matter are released from the nucleus. This spontaneous change in the nucleus is called radioactive decay.
  2. When there is a change in the nucleus and one element changes into another, it is called transmutation.