"Rn" stands for radon in the periodic table. Radon's atomic number is 86, and its atomic weight is 222. Radon was originally called niton when it was discovered in 1900.
Radon is a radioactive, odorless, colorless gas. One of its chief dangers is that it can infiltrate the lower floors of buildings and increase the risk of lung cancer to the occupants. Radon can also be found in water.
Homeowners who fear radon in their homes can learn if they have high levels of the gas through radon detectors. If the levels are high, professional contractors can be called in to remove the radon from the home.