helium 音标拼音: [h'iliəm]
n . 氦
氦
helium n 1 :
a very light colorless element that is one of the six inert gasses ;
the most difficult gas to liquefy ;
occurs in economically extractable amounts in certain natural gases (
as those found in Texas and Kansas ) [
synonym : {
helium }, {
He },
{
atomic number 2 }]
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 ]
Helium \
He "
li *
um \ (
h [=
e ]"
l [
i ^]*[
u ^]
m ),
n . [
NL .,
fr .
Gr . "
h `
lios the sun .] (
Chem .)
An inert ,
monoatomic ,
gaseous element occurring in the atmosphere of the sun and stars ,
and in small quantities in the earth '
s atmosphere ,
in several minerals and in certain mineral waters .
It is obtained from natural gas in industrial quantities .
Symbol ,
He ;
atomic number 2 ;
at .
wt .,
4 .
0026 (
C =
12 .
011 ).
Helium was first detected spectroscopically in the sun by Lockyer in 1868 ;
it was first prepared by Ramsay in 1895 .
Helium has a density of 1 .
98 compared with hydrogen ,
and is more difficult to liquefy than the latter .
Chemically ,
it is an inert noble gas ,
belonging to the argon group ,
and cannot be made to form compounds .
The helium nucleus is the charged particle which constitutes alpha rays ,
and helium is therefore formed as a decomposition product of certain radioactive substances such as radium .
The normal helium nucleus has two protons and two neutrons ,
but an isotope with only one neutron is also observed in atmospheric helium at an abundance of 0 .
013 %.
Liquid helium has a boiling point of -
268 .
9 [
deg ]
C at atmospheric pressure ,
and is used for maintaining very low temperatures ,
both in laboratory experimentation and in commercial applications to maintain superconductivity in low -
temperature superconducting devices .
Gaseous helium at normal temperatures is used for buoyancy in blimps ,
dirigibles ,
and high -
altitude balloons ,
and also for amusement in party balloons .
[
Webster 1913 Suppl .
PJC ]
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