What is the difference between radioactive decay and nuclear transmutation?

In understanding how the atomic world functions, it's essential to grasp the concept of spontaneous nuclear processes. These are nuclear reactions that occur without any external influence. One of the most well-known examples is radioactive decay. Radioactive decay happens without any external provocation. An unstable nucleus will naturally try to achieve stability by emitting radiation, such as alpha particles, beta particles, or gamma rays.

Radioactive decay is a random process at the level of single atoms, meaning that it is impossible to predict exactly when a particular atom will decay. However, for a larger number of atoms, the decay rate is somewhat predictable, characterized by what we call the half-life. The half-life is the time it takes for half of a sample of radioactive material to decay. This property of radioactive decay is widely used for dating archaeological finds, understanding atomic structures, and medical applications in the field of radiology.

Nuclear stability is a crucial aspect of understanding atomic behavior. It refers to the proclivity of an atomic nucleus to remain unchanged. An atomic nucleus consists of protons and neutrons. The forces at play, which include the strong nuclear force and electrostatic repulsion, must be in balance for a nucleus to be considered stable. Protons, which are positively charged, repel each other, but the strong nuclear force, a much stronger but shorter-ranged force, can overcome this repulsion to hold the nucleus together.

A nucleus will be unstable if the forces are not balanced. Generally, isotopes with too many or too few neutrons compared to protons are unstable and prone to radioactive decay. This instability is a core aspect of why certain elements undergo radioactive decay, searching for a more stable configuration. Whether an isotope is stable or not can be predicted using the nuclide, or nuclear, chart. This chart plots the number of protons versus the number of neutrons for known isotopes, with a 'valley of stability' indicating where stable isotopes are likely to be found.

Unlike spontaneous nuclear processes which occur naturally, particle bombardment is an artificial process used to induce change in the nucleus of an atom. This technique involves accelerating particles—neutrons, protons, or larger ions—and colliding them with atomic nuclei. The purpose of particle bombardment is often to induce nuclear transmutation, a non-spontaneous nuclear process in which the number of protons or neutrons in the nucleus of an atom is changed.

This method is used in various fields, such as in the creation of synthetic elements, modifying the properties of materials, and for radiotherapy in medical treatments. The particles used can sometimes be derived from radioactive sources or from particle accelerators. In the context of nuclear medicine, particle bombardment is applied in the synthesis of radioisotopes, which are ultimately used for diagnostics or treatment. For example, bombarding a stable isotope with neutrons can transform it into a radioactive isotope, which can then be used for imaging or cancer treatment.