👉 Polonium is a chemical element that has three isotopes, polonium-210 (94.6% isotopic composition), polonium-211 (8.5%) and polonium-212 (0.5%). Polonium is the lightest known radioactive isotope of the noble gas elements in the periodic table. Poloniums are highly radioactive, with a half-life of about 3.7 billion years. This means that polonium atoms decay over