Definition of Polonium
Po`lo´ni`um
Pronunciation:
pô`lō´nĭ`ŭm
n.
1.
(Chem.)
A
radioactive
chemical
element
,
discovered
by
M
.
and
MMe
.
Curie
in
pitchblende
,
and
originally
called
radium
F
.
It
has
atomic
number
84
and
an
atomic
weight
of
210
.
It
is
a
very
rare
natural
element
,
having
an
abundance
in
uranium
ores
only
0
.
2
%
that
of
radium
.
It
is
closely
related
chemically
to
bismuth
.
It
emits
only
alpha
rays
,
and
has
a
half-life
of
138
days
.
It
is
thus
more
unstable
than
radium
,
and
a
milligram
of
polonium
emits
as
many
alpha
particles
as
5
grams
of
radium
.
Twenty-seven
isotopes
are
known
,
with
atomic
masses
from
192
to
218
.
At
present
a
more
practical
method
of
preparation
than
isolation
from
ores
is
the
preparation
by
neutron
bombardment
of
bismuth
in
a
nuclear
reactor
,
and
it
may
be
obtained
commercially
by
users
having
an
appropriate
permit
.
Related Words
atomic
number
84
,
metal
,
metallic
element
,
Po
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