Polonium is an element with the atomic number 84 and the chemical symbol Po. Its name is derived from Poland, the country of origin of Marie Curie, who discovered the element in 1898. Polonium is a radioactive metal that belongs to the group of elements called the chalcogens. This group includes oxygen, sulfur, selenium, tellurium, and polonium. Polonium is a relatively rare element and is found in uranium ores. It is a highly toxic substance and is considered to be the most radioactive of all the naturally occurring elements.