Polonium the Curies while they were investigating the cause of pitchblende radioactivity. Pitchblende, after removal of the radioactive elements uranium and thorium, was more radioactive than the uranium and thorium combined. This spurred the Curies to search for additional radioactive elements. They first separated out polonium from pitchblende in July 1898, and five months later, also isolated radium. German scientist Willy Marckwald successfully isolated 3 milligrams of polonium in 1902, though at the time he believed it was a new element, which he dubbed "radio-tellurium", and it was not until 1905 that it was demonstrated to be the same as polonium.
Polonium a volatile liquid at room temperature prone to dissociation; it is thermally unstable. Water is the only other known hydrogen chalcogenide which is a liquid at room temperature; however, this is due to hydrogen bonding. The two oxides PoO and PoO are the products of oxidation of polonium. Halides of the structure PoX, PoX and PoF are known. They are soluble in the corresponding hydrogen halides, i.e., PoCl in HCl, PoBr in HBr and PoI in HI. Polonium dihalides are formed by direct reaction of the elements or by reduction of PoCl with SO and with PoBr with HS at