Actinium is a rare and highly radioactive element that has various applications in nuclear science and medicine. It is found in small quantities in uranium and thorium minerals. Actinium can emit alpha, beta, and gamma radiation. One of its isotopes, Actinium-225, has the ability to selectively kill cancer cells, making it a potential breakthrough in cancer therapy. It is also used as a neutron source in nuclear reactors and is produced as a byproduct in the production of radium.