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Discovered
: by Sir William Ramsay
in London, and independently
by P.T. Cleve and N.A.
Langlet in Uppsala, Sweden
in 1895
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Helium
gas is a colourless, odourless,
tasteless inert
gas at room temperature and
makes up about 0.0005% of
the air we breathe.
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During
World War II, the army
and navy funded experimental
plants that produced non-explosive
helium as a replacement
for the explosive hydrogen
gas used in observation
balloons and airships.
Once widely
available, the element
became crucial in ending
the war.
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Manhattan
Project scientists used helium
to make the atomic bomb.
Helium was employed in military
hospitals as a lifesaving
anesthetic. Soldiers suffering
with respiratory diseases
were also administered helium.
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Legendary British flying
ace Douglas Bader, while
recovering from serious wounds
sustained during a dogfight
over France, was treated
with copious amounts of helium.
Upon his triumphant return
to the skies, Bader reputedly
turned to his copilot and
said, Hey Ben... Ben...Wanna
see my Fokker?
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In the liquid state, it
is used to achieve extremely
low temperatures in electronic
devices or for studies in
the region of 0-5 K. Helium
is also the adequate gas
for low temperature gas thermometers
due to its low boiling point
and almost ideal behaviour.
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Helium is also used, mixed
with oxygen, in asthma treatment
because it diffuses very
easily through the lungs.
It can also be used in respiratory
mixtures for high depth divers,
because it is less soluble
in blood than nitrogen.
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Helium
was also found very low
quantities in rocks,
natural and vulcan ic gases
and radioactive minerals.
Helium was initially used
in dirigible-balloons. Nowadays,
is used just like argon,
in the production of an inert
gaseous atmosphere during
magnesium, aluminium and titanium
welding; it can be used in
the cooling of nuclear reactors
as transfer media, since
it is an inert gas.
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The
discovery of helium in
radioactive materials
was not totally understood
until the discovery of radium
in 1898. Then, it was verified
that helium was a stable
product of the radioactive
elements disintegration.
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Some scientists concluded
that the helium
gas present in Earth had
that origin. Some others
thought
that the origin of helium
on Earth was a survival
of the "primordial
helium".
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Helium has a characteristic
and bright spectrum that
easily identifies the element.
Its bright yellow spectrum
stripe, responsible for the
discovery of the element,
is not hidden by any other
element. Scientifically,
helium is one of the most
important elements.
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A helium atom has two protons
in its nucleus and two electrons
around it. Helium nuclei
were created during the big
bang and so are some of the
oldest and commonest objects
in the Universe. About one
quarter of the mass of the
Universe is made up of helium
atoms!
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Helium has some very unusual
properties when it is very
cold. It can flow up the
walls of containers and escape.
It can conduct heat and electricity
with almost no resistance,
making it a superconductor.
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It
is a fact, because of
their unreactivity, the
noble
gases
were not discovered until
the existence of helium
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Because
helium does not burn readily
like hydrogen,
it is a popular gas for lighter-than-air
balloons. Interestingly,
we can recognize the presence
of helium due to its unusual
effects on the vocal chords
.
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In
a helium-rich atmosphere,
a person temporarily experiences
a high-pitched, squeaky
voice. Furthermore, this
gas diffuses easily through
the lungs, and therefore,
it is commonly mixed with
oxygen to create an artificial
air supply for deep-sea
divers.
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Helium never crystallizes
at the normal pressure. Quantum
fluctuations are strong in
Helium due to its low atomic
weight. The interaction of
Helium atoms is weak since
it is a noble gas. As a result,
Helium remains liquid even
at absolute zero. When cooled
to almost absolute zero,
it becomes a super fluid.
Super fluid Helium has zero
viscosity.
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Terrestrial
Effects - Ice ages occur
periodically on Earth and
it has been
suggested that reductions
in the solar luminosity
or some other solar variation
may be partially responsible.
If this is so, then a helium
3 instability which causes
mixing in the solar core
at discrete intervals could
be the cause of periodic
ice ages on Earth.
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The
time between theoretical
core-mixing episodes in
the Sun caused by the helium
3 instability and the intervals
between major ice ages
on the Earth are roughly
similar
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Energy
Generation in the Sun -
The Sun produces energy
by
fusing hydrogen to helium.
This may be accomplished
in a number of ways but in
the Sun, a process known
as the proton-proton chain
is thought to be primarily
responsible for energy generation
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Helium
in the rocks - Most helium
on earth is produced
by radioactive decay in
rocks. The small atoms
of helium gas have no trouble
escaping from the rocks
into the atmosphere.
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Scientists
can work out how fast helium
is forming,
how fast it escapes from
rocks, how much enters
the air, and how much can
escape from the air into
space. They can also measure
the amount of helium in
rocks and in the air. From
this, they can calculate
the maximum age of rocks
and of the air. The results
are puzzling to those who
believe in billions of
years.
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Of
course, all such calculations
depend on assumptions about
the past, like the starting
conditions and constant
rates of processes. They
can never prove the age
of something. For that,
we need an eye-witness
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On
earth, it is produced mainly
by radioactive alpha
(a)-decay. The great New
Zealand physicist Ernest
Rutherford (1871–1937)
discovered that a-particles
were really the nuclei of
helium atoms. Radioactive
elements in rocks—like
uranium and thorium—produce
helium this way, and it leaks
out into the air
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Helium in the sun is generally
believed to be formed by
nuclear fusion. This is where
nuclei of hydrogen, the lightest
element, combine to form
helium with huge amounts
of energy released.
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Helium
is the second lightest
chemical element, with
many
unique properties. It is
so named because it was first
detected in light patterns
in the sun (Greek helios)
before it was detected on
earth. All gases will condense
into a liquid if cooled enough,
but helium has the lowest
condensation point of any
substance (–269°C
or –452°F).
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Unlike
other elements, it will
never freeze, no matter
how cold it is, except
under high pressure.1 Also,
liquid helium cooled below –271°C
(–456°F) forms
a unique phase called a
super fluid, which flows
perfectly, without any
resistance (viscosity).2
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We’re
all familiar with helium,
the very light gas that
makes balloons and airships
float in the air. Helium
has an important safety
advantage—it cannot
burn or explode like hydrogen.
It is also a vital part
of air mixtures for breathing
by deep-sea divers—unlike
nitrogen, it hardly dissolves
in blood or lipids (fatty
compounds) even at high
pressures
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This
avoids nitrogen narcosis,
where the nervous system
(60% lipid) becomes saturated
with nitrogen, which can
make divers feel as if they
had consumed one martini
per 100 ft of depth. It also
avoid the bends or decompression
sickness, a painful and dangerous
condition caused by nitrogen
bubbles forming in the diver’s
blood, nervous system, joints,
and under the skin, if the
pressure drops too fast as
the diver re-surfaces.
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The
helium/oxygen mixture (heliox)
makes the voice very high-pitched,
because sound travels much
faster in helium than in
air—a favourite party
trick using helium-filled
balloons.
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So
why are helium and hydrogen
so much lighter than air?
It's because the hydrogen
and helium atoms are lighter
than a nitrogen atom. They
have fewer electrons, protons
and neutrons than nitrogen
atoms do, and that makes
them lighter (the approximate
atomic weight of hydrogen
is 1, helium is 4 and nitrogen
is 14).
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Approximately
the same number of atoms
of each of these elements
fills approximately the
same amount of space. Therefore,
the gases made of lighter
atoms are lighter. |
hélium
elio
Helium
