Radon- (Symbol Rn , Atomic number 86 )(From radium; called niton at
first, L. nitens, shining) The element was discovered in 1900 by
Dorn, who called it radium emanation. In 1908 Ramsay and Gray, who
named it niton, isolated the element and determined its density,
finding it to be the heaviest known gas. It is essentially inert and
occupies the last place in the zero group of gases in the Periodic
Table. Since 1923, it has been called radon. Twenty isotopes are
known. Radon[222], from radium, has a half-life of 3.823 days and is
an alpha emitter; Rn[220], emanating naturally from thorium and
called thoron, has a half-life of 55.6 s and is also an alpha
emitter. Rn[219] emanates from actinium and is called actinon. It
has a half-life of 3.96 s and is also an alpha emitter. It is
estimated that every square mile of soil to a depth of 6 inches
contains about 1 g of radium, which releases radon in tiny amounts
into the atmosphere. Radon is present in some spring waters, such as
those at Hot Springs, Arkansas. On the average, one part of radon is
present in 1 E21 part of air. At ordinary temperatures radon is a
colorless gas; when cooled below the freezing point, radon exhibits
a brilliant phosphorescence which becomes yellow as the temperature
is lowered and orange-red at the temperature of liquid air. It has
been reported that fluorine reacts with radon, forming a fluoride.
Radon clathrates have also been reported. Radon is still produced
for therapeutic use by a few hospitals by pumping it from a radium
source and sealing it in minute tubes, called seeds or needles, for
application to patient. This practice has been largely discontinued
as hospitals can get the seeds directly from suppliers, who make up
the seeds with the desired activity for the day of use. Care must be
taken in handling radon, as with other radioactive materials. The
main hazard is from inhalation of the element and its solid
daughters which are collected on dust in the air. Good ventilation
should be provided where radium, thorium, or actinium is stored to
prevent build-up of the element. Radon build-up is a health
consideration in uranium mines. Recently radon build-up in homes has
been a concern. Many deaths from lung cancer are caused by radon
exposure. .....
History
of Radon - Screen shot from CHEMIX
School.
