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 |
|
|
|
|
|
|
POLONIUM (Poland, native country of Mme. Curie),
Po; at. mass. (~2l0); at. no.84; m.p. 2540C; b.p. 9620C;
sp. gr. (alpha modification) 9.32; valence -.2,0, + 2, + 3(?),
+ 4, and +6. Polonium was the first element discovered by
Mme. Curie, in 1898, while seeking the cause of radio-
activity of pitchblende from Joachimsthal, Bohemia. The
electroscope showed it separating with bismuth. Polonium
is also called Radium F. Polonium is a' very rare natural
element. Uranium ores contain only about 100 micrograms
of the element per ton. Its abundance is qnty about 0.2%
of that of radium. In 1934 it was found that when natural
bismuth (Bi209) was bombarded by neutrons, Bi210, the
parent of polonium, was obtained. Milligram amounts of
polonium may now be prepared this way, by using the' high
neutron fluxes of nuclear reactors. Polonium-2 10 is a low-
melting, fairly volatile metal, 50% of which is, vaporized in
air in 45 hours at 550C. It is an alpha-emitter with a half-life
of 138.39 days. A milligram emits as many alpha particles
as 5 grams of radium. The energy released by its decay is so
THE ELEMENT~Contiiiued)
large (27.5 calories per curie per day or 140 watts/gm.) that
a capsule containing about half a gram reaches a temperature
above 5000C. The capsule also presents a contact gamma-
ray dose rate of 1.2 roentgens per hour. a A few curies of
polonium exhibit a blue glow, caused by excitation of the
surrounding gas. Because almost all alpha radiation is
stopped within the solid source and its container, giving up
its energy, polonium has attracted attention for uses as a
light-weight heat source for thermoelectric power in space
satellites. Polonium has more isotopes than any other el-
ement. Thirty-four isotopes of polonium are known, with
atomic masses ranging from 192 to 218. Polonium-210 is the
most readily available. Isotopes of mass 209 (half-life of
103 yrs.) and mass 208 (half-life 2.9 yrs.) can be prepared
by alpha, proton, or deuteron bombardment of lead or
bismuth in a cyclotron, but these are expensive to produce.
Metallic polonium has been prepared from polonium hy-
droxide and some other polonium compounds in the pres-
ence ofconcentrated aqueous or anhydrous liquid ammonia.
Two allotropic modifications are known to exist. Polonium
is readily dissolved in dilute acids, but is only slightly soluble
in alkalis. Polonium salts of organic acids char rapidly;
halide ammines are reduced to the metal. Polonium can be
mixed or alloyed with beryllium to provide a source of
neutrons. It has been used in devices for eliminating static
charges in textile mills, etc.; however, beta sources are more
commonly used and are less dangerous. It is also used on
brushes for removing dust from photographic films. The
polonium for these is carefully sealed and controlled, mini-
mizing hazards to the user. Polonium-210 is very dangerous
to handle in even milligram or microgram amounts and
special equipment arid strict control is' necessary. Damage
arises from the complete adsorption of the energy of the alpha
particle into tissue. The maximum permissible body-burden
for ingested polonium is only 0.03 micro~uries, which repre-
sents a particle weighing only 6.8 x 10-12 grams. Weight-
for-weight it is about 2.5 x loll times as toxic as hydro-
cyanic acid. The maximum allowable concentration for
soluble polonium compounds in air is about 2 x 1011
microcuries/oc. Poloniuni is available commercially on
special order with an A.E.C. permit from the Oak Ridge
National Laboratory.
© 1999 F. Davies
Delphi O.E.M. Co.
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