Rn, or Radon, is a colorless, odorless, and tasteless noble gas that occurs naturally in the environment. It is produced from the decay of uranium and thorium found in soil, rock, and water. Radon is radioactive and can pose health risks, particularly when accumulated in enclosed spaces like homes. Due to its radioactive properties, Rn is measured in picocuries per liter (pCi/L) to assess exposure levels. Long-term exposure to high concentrations of radon can lead to lung cancer, making it important for homeowners to test for radon levels and take necessary mitigation steps if needed.