The longest lived, and most common, isotope of radium is 226Ra with a half-life of 1600 years.
226Ra occurs in the decay chain of 238U (often referred to as the radium series).
In the early history of the study of radioactivity, the different natural isotopes of radium were given different names, as it was not until Frederick Soddy's scientific career in the early 1900s that the concept of isotopes was realized.
[3] In this scheme, 223Ra was named actinium X (AcX), 224Ra thorium X (ThX), 226Ra radium (Ra), and 228Ra mesothorium 1 (MsTh1).
No fission products have a half-lifein the range of 100 a–210 ka ... ... nor beyond 15.7 Ma[16]