[{"from": "human", "value": "Provide a brief overview of this molecule. [Rn]"}, {"from": "gpt", "value": "The molecule is the chemical element of symbol Rn and atomic number 86. It is a rare radioactive gas, belonging to the noble gas series, and is formed as part of three radioactive decay chains that begin with uranium or thorium. Thirty-six radioactive isotopes of radon, with mass number from 193 to 228, have been characterized. The most stable isotope is Rn-222 (half-life of 3.8 days); it is generated naturally by the decay of 238U and emits alpha particles. Rn-220 (half-life of 55.6 seconds) is a natural decay product of thorium and also emits alpha radiation. Because of its radioactivity and unreactivity as a chemical element, radon has few uses and is seldom used in academic research. Radon is responsible for the majority of the mean public exposure to ionizing radiations. It is one ingredient of cigarette. (L1075)"}]