The gaseous element radon (Rn) gets attention largely because it's radioactive. Radon is the heaviest and only radioactive member of the group of elements called the noble or inert gases. People have found various uses for radon since its discovery around 1900. For years, many people believed that radon had health benefits and intentionally exposed themselves to small amounts of it. However, radon is now best known as one of the principal causes of lung cancer. Readers investigate the radioactive noble gas, its atomic structure, and its place among the other elements on the periodic table. They'll explore the process of radioactive decay and learn about the many uses and dangers of radon, as well as the steps to take to reduce radon concentrations in the home.