Radon

Radon is a radioactive noble gas that you cannot see, smell, or taste — and it is the second leading cause of lung cancer after smoking. Discovered in 1900 by Friedrich Ernst Dorn, radon seeps up from uranium-containing rocks and soil and can accumulate in basements and ground floors of buildings. About 21,000 lung cancer deaths per year in the US are linked to radon exposure.

Despite its dangers, radon was once considered therapeutic — in the early 1900s, people bathed in radon-infused 'health' springs and even drank radium water! Today, radon testing kits are widely available and recommended for homeowners. Radon is the densest gas known at standard conditions and was initially called 'niton' from the Latin word for shining, because it glows in the dark.

Radon's symbol 'Rn' is a distinctive two-letter element in Spellement. While 'rn' is uncommon at word beginnings, partial emphasis allows spellers to use 'r' or 'n' individually — both among the most frequent consonants in English, providing excellent flexibility for word construction.