radon 音标拼音: [r'ed
, ɑn]
n . 氡
氡
radon n 1 :
a radioactive gaseous element formed by the disintegration of radium ;
the heaviest of the inert gasses ;
occurs naturally (
especially in areas over granite )
and is considered a hazard to health [
synonym : {
radon }, {
Rn }, {
atomic number 86 }]
Noble \
No "
ble \,
a . [
Compar . {
Nobler };
superl . {
Noblest }.] [
F .
noble ,
fr .
L .
nobilis that can be or is known ,
well known ,
famous ,
highborn ,
noble ,
fr .
noscere to know .
See {
know }.]
1 .
Possessing eminence ,
elevation ,
dignity ,
etc .;
above whatever is low ,
mean ,
degrading ,
or dishonorable ;
magnanimous ;
as ,
a noble nature or action ;
a noble heart .
[
1913 Webster ]
Statues ,
with winding ivy crowned ,
belong To nobler poets for a nobler song . --
Dryden .
[
1913 Webster ]
2 .
Grand ;
stately ;
magnificent ;
splendid ;
as ,
a noble edifice .
[
1913 Webster ]
3 .
Of exalted rank ;
of or pertaining to the nobility ;
distinguished from the masses by birth ,
station ,
or title ;
highborn ;
as ,
noble blood ;
a noble personage .
[
1913 Webster ]
Note :
Noble is used in the formation of self -
explaining compounds ;
as ,
noble -
born ,
noble -
hearted ,
noble -
minded .
[
1913 Webster ]
{
Noble gas } (
Chem .),
a gaseous element belonging to group VIII of the periodic table of elements ,
not combining with other elements under normal reaction conditions ;
specifically , {
helium }, {
neon }, {
argon }, {
krypton },
{
xenon },
or {
radon };
also called {
inert gas }.
{
Noble metals } (
Chem .),
silver ,
gold ,
and platinum ; --
so called from their resistance to oxidation by air and to dissolution by acids .
Copper ,
mercury ,
aluminium ,
palladium ,
rhodium ,
iridium ,
and osmium are sometimes included .
[
1913 Webster ]
Syn :
Honorable ;
worthy ;
dignified ;
elevated ;
exalted ;
superior ;
sublime ;
great ;
eminent ;
illustrious ;
renowned ;
stately ;
splendid ;
magnificent ;
grand ;
magnanimous ;
generous ;
liberal ;
free .
[
1913 Webster ]
Radon \
Ra "
don \ (
r [=
a ]"
d [
o ^]
n ),
n . (
Chem .)
An intensely radioactive gaseous element produced by the radioactive decay of radium -
226 ,
which is the main isotope of radium found in pitchblende .
Chemically it is an inert noble gas .
Its atomic symbol is Rn .
It has an atomic number of 86 .
The radon isotope produced by decay of radium has an atomic weight of 222 .
017 ,
and this isotope decays by alpha emission with a half -
life of 3 .
82 days .
Numerous other isotopes have been observed ,
all radioactive and all having half -
lives shorter than that of radon -
222 .
Radon was discovered by M .
and Mme .
Curie ,
of Paris ,
in their studies of the radioactive substances in pitchblende .
Radon was originally called {
radium emanation }
or {
exradio }.
[
PJC ]
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