[{"from": "human", "value": "Synthesize a molecule that matches the given characteristics. 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. Radon-220 (half-life of 55.6 seconds) is a natural decay product of thorium and 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. (L1075)"}, {"from": "gpt", "value": "[220Rn]"}]