👉 The term "polonium" is a chemical element that has the symbol Pu and atomic number 92. Polonium has two isotopes, Pu-241 (radioactive) and Pu-243 (non-radioactive), which are both highly radioactive and used in nuclear reactors. It is also known as polonium-241 because it was first discovered to be unstable and could potentially undergo alpha decay to produce a neutron, emitting gamma radiation.