How does a radioactive decay chain produce a series of different elements?

A radioactive decay chain produces a series of different elements because the process involves fundamental changes to the atomic nucleus, which defines an element's chemical identity.1

When an unstable nucleus undergoes alpha decay, it ejects two protons and two neutrons. This reduces the atomic number by two, transforming the atom into a different chemical element. Conversely, in beta decay, a neutron within the nucleus converts into a proton, an electron, and a neutrino. This increases the atomic number by one, again resulting in a new element.12

Because the daughter nucleus produced by these decays is often itself radioactive, it will continue to decay in a sequence known as a decay chain. This process of transmutation continues through successive generations of parent and daughter nuclei until the chain reaches a stable, non-radioactive isotope, such as lead. While gamma decay also occurs, it involves only energy release and does not change the chemical identity of the nucleus.12