Nuclear decay

Nuclear decay is a stochastic process in which the atomic nucleus spontaneously loses energy (E) and changes composition. The time (t) in which half of the number of nuclei (N) decay is called the half-life (t_½). Nuclear decay is described by an exponential function:

N(t) = e^-ln(2)t/t½

In the Figure, this is shown for four groups, each with 4 (left) or 400 (right) nuclei. In the counter at the top, the time runs from 0 to 4 half-lives. At the end of the simulation period, there is an average of about 1/16 of the initial number of nuclei left.

The most common decay modes are:

1. α-decay
   the nucleus emits a helium nucleus
2. β-decay
   the nucleus emits a positively or negatively charged electron, or the nucleus captures an orbital electron
3. γ-decay or internal conversion
   the nucleus emits a γ-photon, or the decay energy is transferred to an orbital electron
4. nuclear fission
   the nucleus breaks asymmetrically into two parts with a mass ratio of about 2:3

Related concepts

• activity
• atom
• decay constant
• electromagnetic radiation
• electron
• half-life
• molecule
• neutrino
• neutron
• positron
• proton
• X-radiation