The Actinium Series refers to a group of radioactive elements that begin with the element Actinium (Ac) and include its decay products. This series is part of the larger category of uranium decay chains and is characterized by the emission of alpha particles. The series progresses through several isotopes, ultimately leading to stable isotopes of lead (Pb). The primary isotope of Actinium is Ac-227, which decays into Thorium-223 and continues through a series of transformations. Each step in the series involves the release of radiation, making these elements important in fields such as nuclear medicine and radiochemistry.