Radioactive Decay

Radioactive decay is the process by which an unstable atomic nucleus losses energy by emitting radiation. This radiation emitted can be in the form of an alpha, beta or gamma particles, which gives name to the three types of radioactive decay: alpha, beta and gamma decay.

Radioactive decay is a stochastic (random) process for each individual atom. It is impossible to predict when a radioactive nucleus will decay. However, we can use a parameter called half-life to describe how likely it is for an atom to decay.

The half-life of an isotope represents the time that it will take for half of the atoms of that isotope to decay into another, more stable, element or isotope. For example, Carbon-14, a radioactive isotope of Carbon, has a half-life of 5,700 years. This means that, if we have some material that contains a certain amount of Carbon-14, after 5,700 years the amount of Carbon-14 will be half of the initial. 50% of the Carbon-14 atoms will have undergone beta decay and will be turned into Nitrogen-14 instead.

Radioactive decay is a process that has many applications. In the case of Carbon-14, it is used to date fossils. We can infer the concentration of Carbon-14 in the past by several indirect methods, and, by measuring the concentration of Carbon-14 in the present, we know how much Carbon-14 is left. Since it is known that the half-life of Carbon-14 is 5,700 years (half of the Carbon-14 will decay in that time), the Carbon-14 that is left in the fossil is a direct indicator of its age. This technique is used worldwide to determine the age of fossils that are up to 50,000 years old.