Mendelevium

Mendelevium sits at the far edge of the actinide series, a fleeting element that exists only in the smallest quantities imaginable. Created in 1955 at the University of California, Berkeley, it was a triumph of Cold War-era nuclear chemistry — proof that scientists could coax nature into producing atoms that had never existed on Earth, then detect and identify a handful of them before they vanished.

Mendelevium has no practical applications outside of nuclear research. Its short half-lives and the vanishingly small amounts that can be produced make it impossible to use in any industrial, medical, or commercial context. Scientists study its nuclear properties and chemistry purely to deepen understanding of how heavy actinide elements behave at the extreme end of the periodic table.

In February 1955, Albert Ghiorso, Bernard Harvey, Gregory Choppin, Stanley Thompson, and Glenn Seaborg bombarded a target of einsteinium-253 with helium ions in Berkeley's cyclotron. The entire experiment produced just 17 atoms of the new element — yet that was enough to confirm its existence. It was the first time any element had been identified from a single-atom-at-a-time synthesis. The team named it mendelevium in honor of Dmitri Mendeleev, the Russian chemist who published the first widely recognized periodic table in 1869. Naming a synthetic superheavy element after Mendeleev carried a symbolic weight: the man who had organized the elements was being immortalized as one himself.

Mendelevium does not exist in nature. Every atom must be manufactured inside a particle accelerator by bombarding a heavy-element target with energetic ions. The quantities produced in any single experiment are measured in individual atoms or, at most, a few hundred atoms — far too little to weigh, see, or handle by any ordinary means.

Only a few mendelevium compounds have been characterized, and all work is done with microscopic quantities in solution. Studies of its aqueous chemistry confirm that Md3+ is the dominant ion, consistent with typical actinide behavior. Some experiments have also detected Md2+, which is unusually stable for an element this heavy. Solid compounds of mendelevium have never been isolated.

• The entire first synthesis of mendelevium produced exactly 17 atoms — a number so small it would be invisible to any microscope ever built.
• Mendelevium was the first element synthesized and identified one atom at a time, pioneering techniques that all subsequent superheavy element discoveries rely on.
• The element is named after Dmitri Mendeleev, the Russian chemist who created the periodic table — making mendelevium one of the few elements named for the person most responsible for the concept of elements themselves.
• Its most stable isotope, Md-258, has a half-life of about 51.5 days, which sounds short but is remarkably long compared to most synthetic actinides.
• Mendelevium's discovery came during the height of the Cold War, and the choice to honor a Russian scientist with an American discovery carried unmistakable diplomatic undertones at the time.