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 trioxide radioactive. Similar work with curium shows that it is easier to achieve higher oxidation states with longer-lived isotopes; thus, it may be easier to obtain Po(VI) (especially polonium trioxide) using the longer-lived polonium-208 or polonium-209. It has been suggested that Po(VI) might be more stabilized in anions such as or , like other high oxidation states. Polonium trioxide Polonium trioxide (also known as polonium(VI) oxide) is a chemical compound with the formula PoO. It is one of three oxides of polonium, the other two being polonium monoxide (PoO) and polonium dioxide (PoO). It is an interchalcogen. It has so far