Polonium chemically resembles bismuth, helping Marie Curie separate it from uranium ore.
Marie and Pierre Curie announced polonium in July 1898 after processing pitchblende residues. Marie’s chemical strategy was to divide the complex ore into fractions and track radioactivity as each fraction was separated. The unknown radioactive substance behaved analytically like bismuth, so she used bismuth chemistry as the guide for concentrating it.
This resemblance was useful because polonium is a member of the same periodic-table group as bismuth and forms compounds with broadly similar chemical behavior. The Curies could therefore expect polonium to accompany bismuth in precipitation and separation steps, even though its radioactivity revealed that another element was present.
Polonium was named for Poland, Marie Curie’s birthplace. Early samples were not pure polonium metal; the evidence initially came from highly radioactive bismuth-associated fractions. The later isolation and characterization of polonium were difficult partly because it occurs only in tiny quantities and its most important isotope, polonium-210, has a half-life of about 138 days. Barium is instead the important chemical analogue in radium separation.