an unstable radioactive factor discovered in 1955 and created artificially only in really small amounts; symbol Md (additionally Mv). It's a transuranic element with atomic number 101. Isotopes 255, 256, 257, and 258 have now been prepared. Md258, the longest-lived, features a half-life of 2 months.
Definition for "mendelevium"
A synthetic radioactive transuranic component of the actinide…