Mendelevium

Mendelevium was the first element created one atom at a time. In 1955 Albert Ghiorso, Bernard Harvey, Gregory Choppin, Stanley Thompson and Glenn Seaborg at Berkeley fired alpha particles at a nearly invisible speck of einsteinium. Over several runs, they detected just 17 atoms of the new element.

They named it after Dmitri Mendeleev, the Russian chemist who created the periodic table, a notable gesture during the Cold War. Mendelevium is still made only in small numbers of atoms, using particle accelerators. Its longest-lived form lasts about 51 days, long enough for chemists to study how it behaves, but it has no uses outside research.