Radium seventh of a gram of radium. One kilogram of the Earth's crust contains about 900 picograms of radium, and one liter of sea water contains about 89 femtograms of radium. Radium was discovered by Marie Sklodowska-Curie and her husband Pierre Curie on 21 December 1898, in a uraninite (pitchblende) sample. While studying the mineral earlier, the Curies removed uranium from it and found that the remaining material was still radioactive. They separated out an element similar to bismuth from pitchblende in July 1898, that turned out to be polonium. They then separated out a radioactive mixture consisting mostly of two
Polonium dioxide Polonium dioxide Polonium dioxide (also known as polonium(IV) 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 trioxide (PoO). It is a pale yellow crystalline solid at room temperature. Under lowered pressure (such as a vacuum), it decomposes into elemental polonium and oxygen at 500 °C. It is the most stable oxide of polonium and is an interchalcogen. At room temperature, polonium dioxide has a face-centered cubic (fluorite) crystal structure; upon heating to high temperatures, it crystallises in the tetragonal crystal system. The