Mendelevium - Md
Atomic Number 101 Mass Number of Most Important Isotope (258)
Electronegativity 1.3 No Natural Isotopes
Discovered by Albert Ghiorso, Glenn T. Seaborg, Bernard Harvey, Gregory Choppin, and Stanley G. Thompson in 1955.
Abbreviated Electron Configuration [Rn] 5f¹³ 6s²