Radon is the last member of the noble gas family, the group of elements that make up Group 18 in the periodic table. Radon has an atomic number of 86, an atomic mass of 222.0176, and a chemical symbol of Rn.

Properties

Radon is a colorless, odorless, tasteless gas with a boiling point of -79.2°F (-61.8°C) and a density of 9.72 grams per liter, making it about seven times as dense as air. Radon condenses to a clear, colorless liquid at its boiling point and then freezes to form a yellow, then orangish red solid. These changes provide a dramatic sight for the observer since radiation emitted by the element causes these colors to glow brilliantly.

Like other members of the noble gas family, radon is almost completely inert. In the early 1960s, a number of chemists found ways of making compounds of some noble gases, including radon...