Element #87, with the symbol Fr. Francium is the exact opposite of stable, decaying in a matter of nanoseconds. Its most stable isotope, Francium-223, decays in only 22 minutes. It is extremely radioactive, and has no uses besides being a space-filler on the periodic table. One could say that it could be used as a weapon, but the fact that only 30 grams of the
stuff can exist on
Earth at a time would rule out that suggestion.
Single Francium atoms are also fiendishly difficult to synthesize. These factors effectively make Francium forever useless and obsolete. Francium was named after
France, where it was discovered in Paris.