mendelevium

A synthetic radioactive transuranic element of the actinide series that has known isotopes with mass numbers ranging from 245 to 262. The isotopes with the longest half-lives are Md-258 (51.5 days) and Md-260 (31.8 days). Atomic number 101; melting point 827°C; valence 2,3. cross-reference: Periodic Table.

an unstable radioactive element discovered in 1955 and produced artificially only in very small quantities; symbol Md (also Mv). It is a transuranic element with atomic number 101. Isotopes 255, 256, 257, and 258 have been prepared. Md258, the longest-lived, has a half-life of two months.

A transuranic chemical element (symbol Md, formerly Mv) with atomic number 101.

a radioactive transuranic element synthesized by bombarding einsteinium with alpha particles (Md is the current symbol for mendelevium but Mv was formerly the symbol)