How does uranium-238 eventually decay into lead-206?

Uranium-238 does not decay into lead-206 in a single step; rather, it undergoes a multistep process known as a radioactive series (or decay chain).12

Throughout this series, the parent nucleus uranium-238 transforms through a sequence of unstable intermediate isotopes until it reaches the stable end product, lead-206. This transformation involves the emission of eight alpha particles and six beta particles.312

• Alpha decay: The nucleus ejects an alpha particle (two protons and two neutrons), which lowers the atomic number by two and the mass number by four.41
• Beta decay: A neutron in the nucleus converts into a proton, emitting an electron and an antineutrino. This increases the atomic number by one while the mass number remains unchanged.41

This chain of successive decays continues until a stable nuclide is achieved. Because these intermediate isotopes have relatively short half-lives, they are continuously replenished by the decay of the long-lived uranium-238 parent.412