Radon is a chemical element, having the chemical symbol Rn. Its atomic number (the number of protons) is 86. It has a standard atomic weight of 222 g•mol −1 and is a solid in its elemental form.
Radon is a monatomic noble gas. At a pressure of 101.325 kPa, it has a boiling point of −71 °C and a melting point of −61.7 °C.