(From
radium) A heavy,
radioactive,
gaseous chemical element, one of the
noble gases, generated by the
radioactive decay of
radium. Radon decays into
polonium and
alpha rays, and this
radiation makes it useful in
radiotherapy. High levels of radon exposure are associated with areas of
granite rock. It can penetrate buildings through floors and walls and accumulate in the
lungs, causing respiratory damage, including
lung cancer.
Symbol: Rn
Atomic number: 86
Atomic weight: 222 (isotope with the longest known half-life)
Density (at 0°C with 1 atmosphere of pressure): 9.73 g/L
Melting point: -71°C
Boiling point: -61.7°C
Most common valence: 0
Ground state electron configuration: [Xe]4f145d106s26p6