What is the process called in which an atomic nucleus decays and emits an alpha particle?

The process in which an atomic nucleus decays and emits an alpha particle is known as alpha decay. During alpha decay, the nucleus loses two protons and two neutrons, which constitutes the alpha particle. This results in the formation of a different element, as the atomic number changes due to the loss of protons. Alpha decay is a common mode of radioactive decay for heavy elements, as it helps them achieve a more stable energy state by reducing their overall mass and charge.

In contrast, beta decay involves the transformation of a neutron into a proton (or vice versa) and the emission of a beta particle, which is an electron or positron. Gamma decay, on the other hand, does not change the number of protons or neutrons in the nucleus; instead, it involves the emission of gamma rays, which are high-energy photons, usually resulting from the nucleus transitioning to a lower energy state. Spontaneous fission is a rarer form of decay where a heavy nucleus splits into two or more lighter nuclei, along with the release of energy and additional neutrons.

The distinction of alpha decay is significant in understanding nuclear reactions and stability, as it highlights the specific characteristics of different radioactive decay processes.