Radon is a colorless, odorless, radioactive noble gas with the chemical symbol Rn and atomic number 86, produced from the natural decay of uranium and thorium in rocks and soil. Discovered in 1900 by German physicist Friedrich Ernst Dorn, radon is the heaviest noble gas and the only one with no stable isotopes – its longest-lived isotope, radon-222, has a half-life of just 3.8 days. This invisible killer seeps from the ground into buildings where it accumulates, becoming the second leading cause of lung cancer after smoking and responsible for about 21,000 deaths annually in the United States alone. Despite its dangers, radon’s unique properties make it useful for tracking groundwater flow, predicting earthquakes, and even in some controversial medical treatments, while its presence in homes has spawned a multi-billion dollar testing and mitigation industry.

Find out about the noble gasses as a group here [Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), Radon (Rn), Oganesson (Og)]. Find a review of the 50 most important industrial gases here.

20 Fun Facts About Radon

Beyond the basics above, what else should we know about Radon? Check out the 20 fun facts below!

1. Radon is 7.5 times heavier than air, making it the densest gas at room temperature and causing it to accumulate in basements.
2. The gas glows with a brilliant yellow color when cooled below -71°C, changing to orange-red as temperature drops further.
3. Granite countertops emit measurable radon, though levels are typically 100 times lower than dangerous concentrations.
4. Radon levels mysteriously spike 10-40% before earthquakes, leading to research on using it for seismic prediction.
5. The element forms no chemical compounds under normal conditions – the only confirmed compound, radon fluoride, decomposes above -60°C.
6. A single gram of radium produces 0.0001 mL of radon gas daily, used to calibrate radiation detection equipment.
7. Radon “daughters” (decay products) are actually more dangerous than radon itself, sticking to lung tissue and emitting radiation.
8. The EPA’s 4 pCi/L action level means 2,000 radioactive atoms are decaying in each liter of air every second.
9. Radon therapy spas in Europe attract thousands who believe radioactive water treats arthritis, despite cancer risks.
10. Houses built on uranium-rich granite can have radon levels 100 times higher than those on sedimentary rock.
11. The gas was originally called “radium emanation” and given the symbol Em before being renamed radon in 1923.
12. Radon dissolves readily in fat, concentrating 100-fold in fatty tissues compared to blood when inhaled.
13. Minnesota has the highest average radon levels in the US due to glacial deposits of uranium-bearing granite.
14. The element costs $4,000 per milliliter when artificially concentrated, making it one of the most expensive substances.
15. Cave explorers face extreme radon exposure – some caves measure 500 times the EPA residential action level.
16. Radon mitigation systems can reverse home air pressure, accidentally drawing in carbon monoxide from attached garages.
17. The noble gas becomes metallic at just 1 GPa pressure, the lowest pressure metallization of any element.
18. Plants absorb radon through roots, with tobacco particularly efficient at concentrating it in leaves.
19. Nuclear weapons tests in the 1950s temporarily doubled global radon levels by fracturing bedrock and releasing trapped gas.
20. Radon-222’s alpha particles travel only 4 cm in air but carry 5.5 MeV of energy, enough to shatter DNA molecules.

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