After polonium, the Curies discovered radium in 1898.
Marie and Pierre Curie announced polonium in July 1898 while studying pitchblende, a uranium-bearing mineral. The residue left after uranium was removed remained unexpectedly radioactive, suggesting that it contained additional unknown elements. Their continued chemical separations revealed a second element, which they announced to the French Academy of Sciences on 26 December 1898.
They named it radium, from a Latin root meaning “ray,” because of its powerful radioactive emissions. Radium was chemically similar to barium, making it especially difficult to separate. The Curies processed large quantities of ore and used repeated crystallization to concentrate tiny amounts of radium compounds.
The discovery announcement came in 1898, but isolating pure radium metal took much longer. In 1910, Marie Curie and André-Louis Debierne reported producing radium metal. Radium later became famous for its glow and early medical applications, although its dangers were not initially understood.