Check the listing for details. Radon Element Cube. Condition: New. Listed at 74.46 USD. Radon Element Cube Made In USA 2x2x2 inches 99.995% Pure Sample Radon's atomic number is 86 and its symbol is Rn. Radon is a radioactive noble gas that occurs naturally for short periods of time as part of radioactive decay chains. The most stable isotope has a half-life of only 3.8 days. Because it occurs naturally in nature, radon gas is typically an individual's largest source of background radiation. It is often produced by common rock and mineral formations as the radium within them decay. This cube display of the element contains radon-producing minerals such as granite which will radioactively decay over time producing trace amounts of radon gas within the sealed glass ampule. Made In USA 2x2x2 inches 99.995% Pure Sample Radon's atomic number is 86 and its symbol is Rn. Radon is a radioactive noble gas that occurs naturally for short periods of time as part of radioactive decay chains. The most stable isotope has a half-life of only 3.8 days. Because it occurs naturally in nature, radon gas is typically an individual's largest source of background radiation. It is often produced by common rock and mineral formations as the radium within them decay. This cube display of the element contains radon-producing minerals such as granite which will radioactively decay over time producing trace amounts of radon gas within the sealed glass ampule.eBay integration by