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 |
|
|
|
|
|
|
RADIUM (L. radius, ray) Ra; at. wt. (226); at. no.88;
m.p. 7000C; b.p. 11400C;sp. gr. 5?; valence 2. Radium was
discovered in 1898 by M. and Mme. Curie in the pitchblende
or uraninite of North Bohemia, in which it occurs. There is
about I Isni. of radium in 7 tons of pitchblende: The element
was isolated in 1911 by Mme. Curie and Debierne by the
electrolysis of a solution of pure radium chloride, employing
a mercury cathode; on distillation in an atmosphere of
hydrogen this amalgam yielded the pure metal. Originally,
radium was obtained from the rich pitchblende ore found
at Joachimsthal, Bohemia. The carnotite sands of Colorado
furnish some radium, but richer ores are found in the
Democratic Republic of Congo and the Great Bear Lake
region of Canada. Radium is present in all uranium minerals,
andcould be extracted, if desired, from the extensive wastes
of uranium processing. Large uranium deposits are located
in Ontario, New Mexico, Utah, Australia, and elsewhere.
Radium is obtained commercially as the bromide or
chloride; it is doubtful if any appreciable stock of the
isolated element now exists. The pure metal is brilliant white
when freshly prepared, but blackens on exposure to air,
probably due to formation of the nitride. It exhibits lumi-
nescence, as do its salts; it decomposes in water and is some-
what more volatile than barium. It is a member of the
alkaline-earth group of metals. Radium imparts a carmine
red color to a flame. Radium emits alpha, beta, and gamma
rays and when mixed with beryllium produces neutrons.
One gram of Ra226 undergoes 3.7 x 1010 disintegrating per
sec The curie is defined as that amount of radioactivity
which has the same disintegration rate as 1 gm. of Ra226.
Sixteen isotopes are now known; radium-226, the common
isotope, has a half-life of 1620 yrs. One gram of radium
produces about 0.0001 milliliter (stp) of elnanation, or radon
gas, per day. This is pumped from the radium and sealed in
minute tubes, which are used in the treatment of cancer and
other diseases. One gram of radium yields about 1000
calories per year. Radium is used in producing self-luminous
paints, neutron sources and in medicine for the treatment
of disease. Some of the more recently discovered radio-
isotopes, such as Co60, are now being used in place of
radium. Some of these sources are much more powerful,
and others are safer to use. Radium loses about I % of its
activity in 25 yrs., being transformed into elements of
lower atomic weight. Lead is a final product of disintegra-
tion. The study of radium has greatly altered our ideas of
the structure of the atom. Radium is a radiological hazard.
(Stored radium should be ventilated to prevent build-up of
radon.) Inhalation, injection, or body exposure to radium
can cause cancer and other body disorders. The recom-
mended maximum allowable concentration for total body
content is 0.1 microgram and exposure to 2 roentgens/mo.
Radium in the form of the chloride or btomide is available
without A.E.C. permit at a cost of about $25 to $50/milli-
gram, plus service charges.
© 1999 F. Davies
Delphi O.E.M. Co.
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