Radium isotopes are variants of the element Radium that have different numbers of neutrons in their atomic nuclei. The most common isotopes are Radium-226 and Radium-228. These isotopes are radioactive and decay over time, emitting radiation in the form of alpha particles. Radium-226 has a half-life of about 1,600 years, while Radium-228 has a shorter half-life of about 5.75 years. Due to their radioactivity, radium isotopes have been used in various applications, including medical treatments and radioluminescent paints, although their use has declined due to safety concerns.