| Symbol | Rn |
| Atomic number | 86 |
| Group | 18 (Noble gases) |
| Period | 6 |
| Block | p |
| Classification | Noble Gas |
| Appearance | Colorless gas, occasionally glows green or red in discharge tubes |
| Color | Colorless |
| Number of protons | 86 p+ |
| Number of neutrons | 136 n0 |
| Number of electrons | 86 e- |
| Phase at STP | Gas |
| Density | 9.73 g/cm3 |
| Atomic weight | 222 u |
| Melting point | 202 K -71.15 °C -96.07 °F |
| Boiling point | 211.5 K -61.65 °C -78.97 °F |
| Heat of vaporization | 16.4 kJ/mol |
| Electronegativity (Pauling Scale) | 2.2 |
| Electron affinity | -68 kJ/mol |
| Oxidation states | 0, +2, +6 () |
| Ionization energies |
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| Discovery | Ernest Rutherford, Robert Bowie Owens (1899) |
| First isolation | William Ramsay, Robert Whytlaw-Gray (1910) |
Discovery of radon Radon was the fifth radioactive element to be discovered, in 1899 by Ernest Rutherford and Robert B. Owens at McGill University in Montreal, after uranium, thorium, radium, and polonium. In 1899, Pierre and Marie Curie observed that the gas emitted by radium remained radioactive for a month. Later that year, Rutherford and Owens noticed variations when trying to measure radiation from thorium oxide. Rutherford noticed that the compounds of thorium continuously emit a radioactive gas that remains radioactive for several minutes, and called this gas "emanation" (from Latin: emanare, to flow out, and emanatio, expiration), and later "thorium emanation" ("Th Em"). In 1900, Friedrich Ernst Dorn reported some experiments in which he noticed that radium compounds emanate a radioactive gas he named "radium emanation" ("Ra Em"). In 1901, Rutherford and Harriet Brooks demonstrated that the emanations are radioactive, but credited the Curies for the discovery of the element. In 1903, similar emanations were observed from actinium by André-Louis Debierne, and were called "actinium emanation" ("Ac Em"). In 1909, Ramsay and Robert Whytlaw-Gray isolated radon and determined its melting temperature and approximate density. In 1910, they determined that it was the heaviest known gas. | |