Types of Nuclear Decay

In this page is a short explanation of each of the different processes by which a nucleus decays.  A generic formula is presented in each case with a sample equation.  There are many different types of nuclear decay, but for our purposes, I have ordered them as either an Alpha, Beta or Gamma decay process.  Jump to the different types by clicking on the icon's below.

 
 

Alpha Decay

Alpha Particle Emission
In this method of decay, an Alpha particle (Helium Nuclei) is ejected from the nucleus, dropping the mass number by 4 and the atomic number by 2.

 

Beta Decay

Beta Minus (Electron) Emission
In this method, the nucleus releases an electron (b-) along with an anti-neutrino (n) decreasing the number of neutrons by one but creating an extra proton. 

As such, the mass number remains constant (as there is still the same number of particles in the nucleus; A), but the atomic number increases by one (Z).
   

Beta Plus (Positron) Emission
In this case, the nucleus releases an positron (b+) along with a neutrino (n) decreasing the number of protons by one but creating an extra neutron. 

As such, the mass number remains constant (as there is still the same number of particles in the nucleus; A), but the atomic number decreases by one (Z).
   

Electron Capture
In an effort to become stable, this form of decay involves the nucleus absorbing an electron from an inner electron shell of the atom.  This electron combines with a proton, and in the process converts it to a Neutron.

Because of this the mass number remains constant (A) but the atomic number drops by one (Z).

 

Gamma Decay

Isomeric Transition / Atomic Rearrangement / Spontaneous Fission
Every Atomic Rearrangement of the nucleus releases a burst of gamma radiation.  In some cases this may occur after a particle is releases (as described above), or by itself in an effort to make the nucleus more stable.

Isomeric Transition is simply the rearrangement of a "metastable" nucleus from a from that initially is unstable to another nuclear arrangement that is stable.  Substances in this category do not release a particle, but rather  a burst of energy (electromagnetic radiation) in assuming their new, stable form.  As such there is no change in the mass or atomic number of these elements. 

Spontaneous Fission is when a nucleus splits apart (not necessarily equally) releasing a burst of gamma radiation.  Sometimes this also results in the release of a number of particles as well.

 

 

Optional Reading

Double Beta Decay
This decay process is similar to the above Beta minus Emission with the exception that instead of releasing a single positron, the nucleus in this case releases two electrons in an effort to become more stable.

Combination Reactions (also Optional Reading)

In these decay reactions a beta particle is released, and then almost immediately followed by the release of another particle.  In this case, the decay actually is a two step process with an intermediate isotope before the final particle is released.

 Positron with a Delayed Alpha Particle Emission
In this decay process, the atom initially releases a beta (+) particle, and then undergoes a second decay by releasing an alpha particle very shortly after.
   

Positron with a Delayed Proton Emission
Similarly, the atom initially releases a beta (+) particle, and then undergoes a second decay by releasing a proton afterwards.
   

Electron with a Delayed Neutron Emission
In the last of these "combination" decay processes, the atom initially releases a beta (-) particle, and then undergoes a second decay by releasing neutron.

All animations are taken from: http://ie.lbl.gov/education/glossary/glossaryf.htm