- Radon is a chemical element, its symbol is Rn and it has an atomic number of 86.
- Radon is a radioactive noble gas, it is colorless, odorless and tasteless.
- When radon is cooled below its freezing point of −96 °F (−71 °C) it emits a bright radiating luminescence that starts out yellow and as the temperature lowers becomes a orangey red color.
- Radon has a melting point of -95 °F (-71 °C) and a boiling point of -79 °F (-61.7 °C).
- Under normal conditions radon is one of the densest and is the heaviest of known gases.
- The radioactive health risk of radon and the fact it costs a lot has made it hard for experimental chemical research to be performed. Therefore very few radon compounds have been found.
- In 1900, German physicist Friedrich Ernst Dorn discovered radon when he found that radium compounds emit a radioactive gas which he called Radium Emanation. In 1908, William Ramsay and Robert Whytlaw Gray isolated radon and figured out its density.
- The naturally occurring decay of the two most common radioactive elements uranium and thorium, produces radium. Decay of radium then produces radon. As radon decays, it produces more radioactive elements called radon daughters or decay products.
- Radon gas and its decay particles can reach very high concentrations inside buildings. This is especially true in lower levels such as basements due to the heaviness of the gas. Thus, radon is considered a significant contaminant to indoor air quality.
- There is a clear link between breathing high concentrations of radon and incidence of lung cancer. After smoking, radon is the 2nd most frequent cause of lung cancer with over 21,000 lung cancer deaths per year in the US alone.
- In the 1940s and 50s very little ventilation in mines meant incidents of lung cancer due to radon exposure was high among miners of uranium and other hard rock materials, especially in the Czech Republic and U.S. This lead to an overhaul of mining ventilation systems around the world.
- Radon naturally occurs in some hot springs and other spring waters.