Radon is a chemical element with the symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas. It occurs naturally in minute quantities as an intermediate step in the normal radioactive decay chains through which thorium and uranium slowly decay into the lead and various other short-lived radioactive elements. By the late 1980s, naturally occurring radon gas had come to be recognized as a potentially serious health hazard.
|Atomic Mass||222 g.mol −1|
|Discovered by||Friedrich Ernst Dorn in 1900|
|Melting point||−71°C, −96°F, 202 K|
|Boiling point||−61.7°C, −79.1°F, 211.5 K|
|Electron configuration||[Xe] 4f145d106s26p6|
Radon was the fifth radioactive element to be discovered, in 1899 by Ernest Rutherford and Robert B. Owens at McGill University in Montreal, after uranium, thorium, radium, and polonium. Radon atoms possess a particularly stable electronic configuration of eight electrons in the outer shell, which accounts for the characteristic chemical inactivity of the element.
Physical Properties of Radon
- It is a colorless, tasteless, odorless gas at standard pressure and temperature and it is the densest noble gas.
- At a temperature below its freezing point, it posses a brilliant yellow phosphorescence.
- It is highly radioactive and chemically unreactive.
- Natural radon consists of three isotopes, one from each of the three natural radioactive-disintegration series (the uranium, thorium, and actinium series).
- It is a member of the zero-valence elements that are called noble gases and is chemically not very reactive.