H' at. wt. (natural) 1.007967
at. wt. (H') 1.007822
at. no. 1
m.p. - 259.140C
b.p. - 252.870C
density 0.08988 gm./l
density (liquid) 70.8 gm/i. (-2530C)
density (solid) 7016 gm/i. (-2620C)
valence 1.
Electronic configuration
| K |
L |
M |
N |
O |
P |
Q |
| 1 |
2 |
3 |
4 |
5 |
6 |
7 |
| s |
s p |
s p d |
s p d f |
s p d f |
s p d f |
s p d f |
| 1 |
|
|
|
|
|
|
RADON (from radium; called niton at first, L. nitens,
shining), Rn; at. wt. (~222); at. no.86; m.p. -710C; b.p.
61.800'; density of gas 9.73 ems/i;, sp. gr. liquid 4.4 at
- 620C, solid 4; valence usually 0. The element was dis-
covered 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 arid 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, coming from radium, has a half4iie
of 3.823 days and is an alpha emitter; radon-220, emanating
naturally from thorium and called thoron, has a halfAife
of 54.5 seconds and is also an alpha emitter. Radon-219,
emanates from actinium and is called actinon. It has a half-
life of 3.92 seconds 'and is also an alpha emitter. It is esti-
mated that every square mile of soil to a depth of 6 inches
contains ahout I gm. of radium, which releases radon in
tiny amounts to the atmosphere. Raddn' is present in some
spring waters, such as those at flot Springs, Arkansas. On
the average, orie part of radon is present to I sextillion parts
of air. At ordinary temperatures radon is a colorless gas;
when c6oled 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 radon 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 applica-
tion to patients. This practice is now largely discontinued as
hospitals can order the seeds directly from suppliers, who
make up the seeds with the desired activity for the day of
use. Radon is available at a cost of about 54/millicurie.
Care must be taken in handling radon, as with other radio-
active materials. The main hazard is from inhalation of the
element and its solid daughters, which are collected on dust
in the air. The maximum permissible level in air has been
given at 10 -' microcuries/milliliter. Good ventilation should
he provided where radium, thorium, or actinium is stored
to prevent buildup of this element. Radon buildup is also a
health considerafion in uranium mines.
© 1999 F. Davies
Delphi O.E.M. Co.
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