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 reaction of two elements. NaPo has the antifluorite structure, the polonides of Ca, Ba, Hg, Pb and lanthanides form a NaCl lattice, BePo and CdPo have the wurtzite and MgPo the nickel arsenide structure. Most polonides decompose upon heating to about 600 °C, except for HgPo that decomposes at ~300 °C and the lanthanide polonides, which do not decompose but melt at temperatures above 1000 °C. For example, PrPo melts at 1250 °C and TmPo at 2200 °C. PbPo is one of the very few naturally occurring polonium compounds, as polonium alpha decays to form lead. Polonium hydride () is