Polonium initiator was classified until the 1960s. The Atomic Energy Commission and the Manhattan Project funded human experiments using polonium on five people at the University of Rochester between 1943 and 1947. The people were administered between of polonium to study its excretion. Polonium is a very rare element in nature because of the short half-life of all its isotopes. Po, Po, and Po appear in the decay chain of U; thus polonium can be found in uranium ores at about 0.1 mg per metric ton (1 part in 10), which is approximately 0.2% of the abundance of radium. The amounts
Polonium hydride and hydrogen selenide, and decomposes into its constituent elements, releasing heat in the process. The amount of heat given off in the decomposition of polonium hydride is over 100 kJ/mol, the largest of all the hydrogen chalcogenides. Polonium hydride is a liquid due to van der Waals forces, and not due to the same reason as why water (hydrogen oxide) is liquid (hydrogen bonding). It is predicted that, like the other hydrogen chalcogenides, polonium may form two types of salts: polonide (containing the Po anion) and one from polonium hydride (containing –PoH, which would be the polonium analogue of thiol,