Radium chloride salt of radioactive element radium. It was first isolated in the early 20th century by Marie Curie and André-Louis Debierne. The most stable isotope is radium-226, it has a half-life of 1600 years and occurs naturally as a product of radioactive decay of uranium. Chloride of radium-223 (half-life 11.4 days) is used in medicine as a radiotherapeutic drug. It was approved for the treatment of male patients with symptoms of advanced prostate cancer with bone metastases. Ra 223 mimics calcium and forms complexes with the bone mineral hydroxyapatite at areas of increased bone turnover. The radioactive alpha particles emitted by radium Ra 223 helps in killing cancer cells in the bone by damaging their DNA. Radium Ra 223 causes minimal damage to the nearby healthy cells.