Mendelevium (Md) is a radioactive, metallic element that is a member of the actinide series; mendelevium is a transuranic element. It was first synthesized in 1955 at the University of California at Berkeley (one atom at a time) by the alpha-particle bombardment of einsteinium-253. Its most stable isotope is ²⁵⁸Md (half-life 2 months). It is named after the Russian pioneer of the periodic table, Dmitri Mendeleyev.