Science / Periodic Table of Elements / Mendelevium (Md): Atomic number: 101, Atomic mass: (258) g.mol -1, Electronegativity: unknown, Density: unknown, Melting point: unknown, Boiling point: unknown, Vanderwaals radius: unknown, Ionic radius: unknown, Isotopes: 1, Electronic shell: [ Rn ] 5f12 6d1 7s2, Discovered by: G.T. Seaborg in 1955. Mendelevium is the first transferium element with the most stable isotope 258Md having a half-life of 52 days. It's chemical data are limited to its atomic number, its haf life and isotopes. Atomic weight of known isotopes range from 245 to 261. It is named after Dimitri Mendeleyev, who produced one of the first periodic tables. Applications: The transferium elements have neither application nor economic role. Mendelevium in the environment: The transferium elements do not exist in nature and they have very unstable nuclei, so they are quite hard to make and detect.