polonium 音标拼音: [pəl'oniəm]
n . 钋
钋
polonium n 1 :
a radioactive metallic element that is similar to tellurium and bismuth ;
occurs in uranium ores but can be produced by bombarding bismuth with neutrons in a nuclear reactor [
synonym :
{
polonium }, {
Po }, {
atomic number 84 }]
Polonium \
Po *
lo "
ni *
um \ (
p [-
o ]*
l [=
o ]"
n [
i ^]*[
u ^]
m ),
n . [
NL .
So named after Poland ,
in L .
form Polonia ,
one of the discoverers being a Pole .] (
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 . --[
HBCF61 ]
[
Webster 1913 Suppl .
PJC ]
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