- Mendelevium (Md) is a synthetic, silvery, radioactive metal with atomic number 101, belonging to the actinide series.
- Its electron configuration is [Rn] 5f¹³ 7s², and it typically exhibits the +3 oxidation state, although +2 can also occur under reducing conditions.
- The atomic structure contains one hundred and one protons, most often one hundred and fifty-seven neutrons in mendelevium-258 (²⁵⁸Md), and one hundred and one electrons arranged in seven shells. Mendelevium does not exist naturally; it is produced in particle accelerators by bombarding lighter actinides such as einsteinium with charged particles.
- The longest-lived isotope is mendelevium-258 (²⁵⁸Md), which has a half-life of about 51.5 days, while most other isotopes decay within hours or minutes.
- Mendelevium was first synthesized in 1955 by a team of American scientists—Albert Ghiorso, Glenn T. Seaborg, Bernard Harvey, Gregory Choppin, and Stanley G. Thompson—at the University of California, Berkeley. The team produced it by bombarding einsteinium-253 (²⁵³Es) with helium ions (alpha particles) using a cyclotron, yielding a single atom of mendelevium-256 (²⁵⁶Md). This was the first time an element had been discovered atom-by-atom, marking a milestone in nuclear science. The element was named in honor of Dmitri Mendeleev, the Russian chemist who created the periodic table.
- Due to its scarcity and short half-life, mendelevium has no commercial applications. Its significance lies in scientific research, particularly in understanding the chemistry of heavy actinides and the limits of the periodic table. Experiments with mendelevium have helped scientists explore trends in electron configurations and oxidation states among the actinides.
- Chemically, mendelevium behaves similarly to other trivalent actinides, forming compounds such as mendelevium(III) chloride (MdCl₃), mendelevium(III) oxide (Md₂O₃), and coordination complexes in aqueous solution. The Md³⁺ ion is stable in water, though reducing conditions can produce Md²⁺, which is of special interest because it reflects the actinide–lanthanide similarities in electron behavior.
- Biologically, mendelevium has no known function and is highly radiotoxic. Even trace exposures could cause cellular damage due to its alpha radiation, but in practice, the amounts produced are so minuscule that biological studies are virtually impossible.
- Environmentally, mendelevium does not occur naturally and exists only where it has been artificially synthesized in particle accelerators. Its rapid decay and extremely limited production mean it has no measurable environmental presence.
