Helium and Radon are both gases that are found in the Earth's atmosphere. Helium is a colorless, odorless, tasteless, non-toxic, inert GAS that is the second most abundant element in the universe. Radon is a radioactive, colorless, odorless, tasteless noble GAS that is the heaviest known GAS and is produced naturally by the decay of uranium and thorium in rocks and soil. Both gases have a variety of uses, including medical applications, industrial processes, and scientific research.