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CAS Number: 7440-59-7
EC Number: 231-168-5

Helium (from Greek: ἥλιος, romanized: helios, lit. 'sun') is a chemical element with the symbol He and atomic number 2. 
Helium is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. 

Helium's boiling and melting point are the lowest among all the elements. 
Helium is the second lightest and second most abundant element in the observable universe (hydrogen is the lightest and most abundant). 

Helium is present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined. 
Helium's abundance is similar to this in both the Sun and in Jupiter, due to the very high nuclear binding energy (per nucleon) of helium-4, with respect to the next three elements after helium. 

This helium-4 binding energy also accounts for why Helium is a product of both nuclear fusion and radioactive decay. 
Most helium in the universe is helium-4, the vast majority of which was formed during the Big Bang. 
Large amounts of new helium are created by nuclear fusion of hydrogen in stars.

Helium was first detected as an unknown, yellow spectral line signature in sunlight during a solar eclipse in 1868 by Georges Rayet, Captain C. T. Haig, Norman R. Pogson, and Lieutenant John Herschel, and was subsequently confirmed by French astronomer Jules Janssen.  

Janssen is often jointly credited with detecting the element, along with Norman Lockyer. 
Janssen recorded the helium spectral line during the solar eclipse of 1868, while Lockyer observed Helium from Britain. 
Lockyer was the first to propose that the line was due to a new element, which he named. 

The formal discovery of the element was made in 1895 by chemists Sir William Ramsay, Per Teodor Cleve, and Nils Abraham Langlet, who found helium emanating from the uranium ore, cleveite, which is now not regarded as a separate mineral species, but as a variety of uraninite. 
In 1903, large reserves of helium were found in natural gas fields in parts of the United States, by far the largest supplier of the gas today.

On Earth, Helium is relatively rare—5.2 ppm by volume in the atmosphere. 
Most terrestrial helium present today is created by the natural radioactive decay of heavy radioactive elements (thorium and uranium, although there are other examples), as the alpha particles emitted by such decays consist of helium-4 nuclei. 

This radiogenic helium is trapped with natural gas in concentrations as great as 7% by volume, from which Helium is extracted commercially by a low-temperature separation process called fractional distillation. 
Terrestrial helium is a non-renewable resource because once released into the atmosphere, Helium promptly escapes into space. 

Helium's supply is thought to be rapidly diminishing. 
However, some studies suggest that helium produced deep in the earth by radioactive decay can collect in natural gas reserves in larger than expected quantities, in some cases, having been released by volcanic activity.

Helium gets Helium's name from ‘helios’, the Greek word for the sun. 
Helium was detected in the sun by its spectral lines many years before it was found on Earth.
A colourless, odourless gas that is totally unreactive.

Below Helium's boiling point of 4.22 K (−268.93 °C; −452.07 °F) and above the lambda point of 2.1768 K (−270.9732 °C; −455.7518 °F), the isotope helium-4 exists in a normal colorless liquid state, called helium I.
Helium-4 is unique in having two liquid forms. 

The normal liquid form is called helium I and exists at temperatures from Helium I's boiling point of 4.21 K (−268.9 °C) down to about 2.18 K (−271 °C). 
Below 2.18 K, thermal conductivity of helium-4 becomes more than 1,000 times greater than that of copper. 

This liquid form is called helium II to distinguish it from normal liquid helium I. 
Helium II exhibits the property called superfluidity: its viscosity, or resistance to flow, is so low that it has not been measured. 

This liquid spreads in a thin film over the surface of any substance it touches, and this film flows without friction even against the force of gravity. 
By contrast, the less plentiful helium-3 forms three distinguishable liquid phases of which two are superfluids. 

Superfluidity in helium-4 was discovered by the Russian physicist Pyotr Leonidovich Kapitsa in the mid-1930s, and the same phenomenon in helium-3 was first observed by Douglas D. Osheroff, David M. Lee, and Robert C. Richardson of the United States in 1972.

A liquid mixture of the two isotopes helium-3 and helium-4 separates at temperatures below about 0.8 K (−272.4 °C, or −458.2 °F) into two layers. 
One layer is practically pure helium-3; the other is mostly helium-4 but retains about 6 percent helium-3 even at the lowest temperatures achieved. 

The dissolution of helium-3 in helium-4 is accompanied by a cooling effect that has been used in the construction of cryostats (devices for production of very low temperatures) that can attain—and maintain for days—temperatures as low as 0.01 K (−273.14 °C, or −459.65 °F).

Below Helium I's boiling point of 4.22 K (−268.93 °C; −452.07 °F) and above the lambda point of 2.1768 K (−270.9732 °C; −455.7518 °F), the isotope helium-4 exists in a normal colorless liquid state, called helium I. 

Like other cryogenic liquids, helium I boils when Helium I is heated and contracts when Helium I's temperature is lowered. 
Below the lambda point, however, helium does not boil, and Helium expands as the temperature is lowered further.

Helium I has a gas-like index of refraction of 1.026 which makes its surface so hard to see that floats of Styrofoam are often used to show where the surface is. 
This colorless liquid has a very low viscosity and a density of 0.145–0.125 g/mL (between about 0 and 4 K), which is only one-fourth the value expected from classical physics. 

Quantum mechanics is needed to explain this property and thus both states of liquid helium (helium I and helium II) are called quantum fluids, meaning they display atomic properties on a macroscopic scale. 
This may be an effect of its boiling point being so close to absolute zero, preventing random molecular motion (thermal energy) from masking the atomic properties.

Liquid helium below Liquid helium's lambda point (called helium II) exhibits very unusual characteristics. 
Due to Liquid helium's high thermal conductivity, when it boils, Liquid helium does not bubble but rather evaporates directly from its surface. 

Helium-3 also has a superfluid phase, but only at much lower temperatures; as a result, less is known about the properties of the isotope.

Helium II is a superfluid, a quantum mechanical state (see: macroscopic quantum phenomena) of matter with strange properties. For example, when it flows through capillaries as thin as 10−7 to 10−8 m it has no measurable viscosity. 

However, when measurements were done between two moving discs, a viscosity comparable to that of gaseous helium was observed. 
Current theory explains this using the two-fluid model for helium II. 

In this model, liquid helium below the lambda point is viewed as containing a proportion of helium atoms in a ground state, which are superfluid and flow with exactly zero viscosity, and a proportion of helium atoms in an excited state, which behave more like an ordinary fluid.

In the fountain effect, a chamber is constructed which is connected to a reservoir of helium II by a sintered disc through which superfluid helium leaks easily but through which non-superfluid helium cannot pass. 

If the interior of the container is heated, the superfluid helium changes to non-superfluid helium. 
In order to maintain the equilibrium fraction of superfluid helium, superfluid helium leaks through and increases the pressure, causing liquid to fountain out of the container.

The thermal conductivity of helium II is greater than that of any other known substance, a million times that of helium I and several hundred times that of copper. 
This is because heat conduction occurs by an exceptional quantum mechanism. 

Most materials that conduct heat well have a valence band of free electrons which serve to transfer the heat. 
Helium II has no such valence band but nevertheless conducts heat well. 
The flow of heat is governed by equations that are similar to the wave equation used to characterize sound propagation in air. 

When heat is introduced, it moves at 20 meters per second at 1.8 K through helium II as waves in a phenomenon known as second sound.
Helium II also exhibits a creeping effect. 

When a surface extends past the level of helium II, the helium II moves along the surface, against the force of gravity. Helium II will escape from a vessel that is not sealed by creeping along the sides until Helium II reaches a warmer region where it evaporates. 

Helium II moves in a 30 nm-thick film regardless of surface material. 
This film is called a Rollin film and is named after the man who first characterized this trait, Bernard V. Rollin. 
As a result of this creeping behavior and helium II's ability to leak rapidly through tiny openings, Helium II is very difficult to confine. 

Unless the container is carefully constructed, the helium II will creep along the surfaces and through valves until Helium II reaches somewhere warmer, where Helium II will evaporate. 

Waves propagating across a Rollin film are governed by the same equation as gravity waves in shallow water, but rather than gravity, the restoring force is the van der Waals force. 
These waves are known as third sound.

There are nine known isotopes of Helium, but only helium-3 and helium-4 are stable. 
In the Earth's atmosphere, one atom is 3
Helium for every million that are 4 He. 

Unlike most elements, helium's isotopic abundance varies greatly by origin, due to the different formation processes. 
The most common isotope, helium-4, is produced on Earth by alpha decay of heavier radioactive elements; the alpha particles that emerge are fully ionized helium-4 nuclei. 

Helium-4 is an unusually stable nucleus because Helium-4's nucleons are arranged into complete shells. 
Helium-4 was also formed in enormous quantities during Big Bang nucleosynthesis.
Helium-3 is present on Earth only in trace amounts. 

Most of Helium-4 has been present since Earth's formation, though some falls to Earth trapped in cosmic dust Trace amounts are also produced by the beta decay of tritium. 
Rocks from the Earth's crust have isotope ratios varying by as much as a factor of ten, and these ratios can be used to investigate the origin of rocks and the composition of the Earth's mantle. 

3 Helium is much more abundant in stars as a product of nuclear fusion. 
Thus in the interstellar medium, the proportion of 3 Helium to 4 Helium is about 100 times higher than on Earth. 

Extraplanetary material, such as lunar and asteroid regolith, have trace amounts of helium-3 from being bombarded by solar winds. 
The Moon's surface contains helium-3 at concentrations on the order of 10 ppb, much higher than the approximately 5 ppt found in the Earth's atmosphere. 

A number of people, starting with Gerald Kulcinski in 1986, have proposed to explore the moon, mine lunar regolith, and use the helium-3 for fusion.
Liquid helium-4 can be cooled to about 1 K (−272.15 °C; −457.87 °F) using evaporative cooling in a 1-K pot. 

Similar cooling of helium-3, which has a lower boiling point, can achieve about 0.2 kelvin in a helium-3 refrigerator. 
Equal mixtures of liquid 3 He and 4 He below 0.8 K separate into two immiscible phases due to their dissimilarity (they follow different quantum statistics: helium-4 atoms are bosons while helium-3 atoms are fermions). 

Dilution refrigerators use this immiscibility to achieve temperatures of a few millikelvins.
It is possible to produce exotic helium isotopes, which rapidly decay into other substances. 
The shortest-lived heavy helium isotope is the unbound helium-10 with a half-life of 2.6(4)×10−22 s. 

Helium-6 decays by emitting a beta particle and has a half-life of 0.8 second. 
Helium-7 also emits a beta particle as well as a gamma ray. 

Helium-7 and helium-8 are created in certain nuclear reactions. 
Helium-6 and helium-8 are known to exhibit a nuclear halo.

Helium has a valence of zero and is chemically unreactive under all normal conditions. 
Helium is an electrical insulator unless ionized. 
As with the other noble gases, helium has metastable energy levels that allow Helium to remain ionized in an electrical discharge with a voltage below Helium's ionization potential. 

Helium can form unstable compounds, known as excimers, with tungsten, iodine, fluorine, sulfur, and phosphorus when Helium is subjected to a glow discharge, to electron bombardment, or reduced to plasma by other means. 
The molecular compounds HeNe, HgHe10, and WHe2, and the molecular ions He+ 2, He2+ 2, HeH+,  and HeD+ have been created this way. 

HeH+ is also stable in its ground state, but is extremely reactive—it is the strongest Brønsted acid known, and therefore can exist only in isolation, as it will protonate any molecule or counteranion it contacts. 
This technique has also produced the neutral molecule He2, which has a large number of band systems, and HgHe, which is apparently held together only by polarization forces.

Van der Waals compounds of helium can also be formed with cryogenic helium gas and atoms of some other substance, such as LiHe and He2.
Theoretically, other true compounds may be possible, such as helium fluorohydride (HHeF) which would be analogous to HArF, discovered in 2000. 

Calculations show that two new compounds containing a helium-oxygen bond could be stable. 
Two new molecular species, predicted using theory, CsFHeO and N(CH3)4FHeO, are derivatives of a metastable FHeO− anion first theorized in 2005 by a group from Taiwan. 
If confirmed by experiment, the only remaining element with no known stable compounds would be neon.

Helium atoms have been inserted into the hollow carbon cage molecules (the fullerenes) by heating under high pressure. 
The endohedral fullerene molecules formed are stable at high temperatures. 
When chemical derivatives of these fullerenes are formed, the helium stays inside. 

If helium-3 is used, it can be readily observed by helium nuclear magnetic resonance spectroscopy. 
Many fullerenes containing helium-3 have been reported. 

Although the helium atoms are not attached by covalent or ionic bonds, these substances have distinct properties and a definite composition, like all stoichiometric chemical compounds.

Under high pressures helium can form compounds with various other elements. 
Helium-nitrogen clathrate (He(N2)11) crystals have been grown at room temperature at pressures ca. 10 GPa in a diamond anvil cell. 

The insulating electride Na2He has been shown to be thermodynamically stable at pressures above 113 GPa. 
It has a fluorite structure.

Helium gets Helium's name from ‘helios’, the Greek word for the sun. 
Helium was detected in the sun by Helium's spectral lines many years before Helium was found on Earth.
A colourless, odourless gas that is totally unreactive.

Helium has been a low price resource for many years leading to Helium's ineficient utilization. 
Helium is now a scarce resource and Helium's prices are increasing significantly.
Therefore, solutions for Helium recovery and purification are needed. 

Helium recovery alone is not the answer to this problem, as Helium purity decreases at each process cycle and needs to be released when minimum purity level is reached. 
Helium (He), chemical element, inert gas of Group 18 (noble gases) of the periodic table. 

The second lightest element (only hydrogen is lighter), helium is a colourless, odourless, and tasteless gas that becomes liquid at −268.9 °C (−452 °F). 
The boiling and freezing points of helium are lower than those of any other known substance. 

Helium is the only element that cannot be solidified by sufficient cooling at normal atmospheric pressure; Helium is necessary to apply pressure of 25 atmospheres at a temperature of 1 K (−272 °C, or −458 °F) to convert Helium to its solid form.
Helium is the second-lightest element. 

Although Helium is rare on Earth, you likely have encountered it in helium-filled balloons. 
In addition to being rare, helium is (mostly) not a renewable resource. 
The helium that we have was produced by the radioactive decay of rock, long ago. 

Over the span of hundreds of millions of years, Helium accumulated and was released by tectonic plate movement, where Helium found Helium's way into natural gas deposits and as a dissolved gas in groundwater. 

Once the gas leaks into the atmosphere, Helium is light enough to escape the Earth's gravitational field so it bleeds off into space, never to return. 
We may run out of helium within 25–30 years because Helium's being consumed so freely.

All but two-ten thousandths of one percent of the Earth's supply of naturally occurring helium atoms are the type known as helium-4. 
They contain 2 protons and 2 neutrons. 
But the other 0.0002 percent of are known as helium 3. 

These rare examples of the element contain just one neutron. 
Helium 3 can help cool things down beyond helium-4's 4 Kelvin limit, enabling scientists to study the fundamental properties of materials to within a few thousandths of a Kelvin above absolute zero.

Virtually all helium-3 being used today is produced in nuclear reactors. 
Helium 3's not cheap. 
Only about 6,000 liters, or a mere 1.5 pounds of helium-3, is produced in the U.S. each year. 
Helium's price tag is as much as $2,000 per liter, or more than 400 times the price of gold by weight today. 

The material is so precious that scientists have proposed mining it on the moon, from deposits brought there over billions of years via the solar wind. 
The process was fictionally depicted in the 2009 film, "Moon". 

NASA astronaut and geologist Harrison Schmidt has himself suggested mining lunar helium-3 deposits; other researchers have pointed to Saturn, Jupiter, and distant asteroids as possible additional sources of helium-3.
Several nations including China and India are developing plans to send spacecraft to the moon to investigate mining opportunities. 

But helium mining is not necessarily the top priority for the U.S. 
"NASA is very interested in getting back to the lunar surface," said Noah Petro, a lunar geologist and research scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. 
"But so far," he continued, "helium-3 extraction is not one of the primary objectives for our immediate return."

In 1908, Dutch physicist Heike Kamerlingh Onnes managed to liquefy helium for the first time. 
Helium is also the first superfluid ever discovered. 
When cooled below 2.17 Kelvin, its viscosity – a parameter for measuring the thickness of a liquid – becomes zero. 

This gives helium freaky, superfluid properties, such as being able to sustain a vortex forever and to creep up the surface of a bowl and drip down its side.

"It was a wonderful sight when the liquid, which looked almost unreal, was seen for the first time. 
It was not noticed when it flowed in. 
Its presence could not be confirmed until it had already filled up the vessel. 
Its surface stood sharply against the vessel like the edge of a knife," said Onnes during the lecture he gave in 1913 upon receiving the 1913 Nobel Prize in Physics.

Gaseous chemical element, symbol: He, atomic number: 2 and atomic weight 4,0026 g/mol. 
Helium is one of the noble gases of group O in the periodic table. 
Helium’s the second lightest element. 
The main helium source in the world is a series of fields of natural gas in the United States.

Helium is a colourless, odourless, insipid and non-toxic gas. 
Helium’s less soluble in water than any other gas. 
Helium’s the less reactive element and doesn’t essentially form chemical compounds. 

The density and viscosity of helium vapour are very low. 
The thermic conductivity and the caloric content are exceptionally high. 
Helium can be liquefied, but Helium's condensation temperature is the lowest among all the known substances.

Helium is the second most abundant element in the known universe, after hydrogen. 
Helium constitutes the 23% of all elemental matter measured by mass. 
Helium is formed in The Earth by natural radioactive decay of heavier elements. 

Most of this helium migrates to the surface and enters the atmosphere. 
Helium could be logical to think that the helium concentration in the atmosphere was higher than Helium is (5,25 parts per million at sea level). 
Nevertheless, Helium's low molecular weight allows Helium to escape to space at the same rate of its formation. 

There is an about 1000 km layer in the heterosphere at 600 miles where helium is the dominant gas (although the total pressure is very low). 
Natural gases contain higher helium concentrations than the atmosphere.
Helium is the 71st most abundant element in the Earth's crust where Helium is found in 8 parts per billion.

Helium atoms have 2 electrons and the shell structure is 2. 
The ground state electronic configuration of neutral helium is 1s2 and the term symbol of helium is 1S0.
Helium is one of the so-called noble gases. 
Helium gas is an unreactive, colourless, and odourless monoatomic gas. 

Helium is available in pressurised tanks.
Helium is the second most abundant element in the universe after hydrogen. α-particles are doubly ionised helium atoms, He2+.
Helium is used in lighter than air balloons and while heavier than hydrogen, is far safer since helium does not burn. 

Speaking after breathing an atmosphere rich in helium results in a squeaky voice (don't try it!).
Helium is present in the atmosphere at about 0.0005% (1 part in 200000) by volume and is an important component within hydrocarbon gases in the USA. 
Helium's origin in these gases is traced to the decay of radioactive elements in rocks.

Isolation: there is very little helium on earth as nearly all present during and immediately after the earth's formation has long since been lost as Helium is so light. 
Just about all the helium remaining on the planet is the result of radioactive decay. 

While there is some helium in the atmosphere, currently its isolation from that source by liquefaction and separation of air is not normally economic. 
This is bacause Helium is easier, and cheaper, to isolate the gas from certain natural gases. 

Concentrations of helium in natural gas in the USA are as high as 7% and other good sources include natural gas from some sources in Poland. 
Helium is isolable from these gases by liquefaction and separation of from the natural gas. 
This would not normally be carried out in the laboratory and helium is available commercially in cylinders under pressure.

Helium is found in minute proportions in the atmosphere, less than 0.001% in air. 
Helium can also be found in a certain number of natural gas fields, where Helium results from the natural radioactive decay of heavy elements in the earth’s crust, in particular, uranium and thorium. 

It is helium extracted from the natural gas fields where the concentration is greater than 0.1% which is sold in liquid and gaseous forms today.
Helium gas (98.2 percent pure) is isolated from natural gas by liquefying the other components at low temperatures and under high pressures. 

Adsorption of other gases on cooled, activated charcoal yields 99.995 percent pure helium. 
Some helium is supplied from liquefaction of air on a large scale; the amount of helium obtainable from 1,000 tons (900 metric tons) of air is about 112 cubic feet (3.17 cubic metres), as measured at room temperature and at normal atmospheric pressure.

The primary source of helium is from natural gas wells. 
Helium is obtained by a liquefaction and stripping operation.
Due to the world shortage in helium, many applications have recovery systems to reclaim the helium.

In 2008, approximately 169 million standard cubic meters (SCM) of helium were extracted from natural gas or withdrawn from helium reserves with approximately 78% from the United States, 10% from Algeria, and most of the remainder from Russia, Poland and Qatar. 

By 2013, increases in helium production in Qatar had increased Qatar's fraction of world helium production to 25%, and made it the second largest exporter after the United States. 
An estimated 54 billion cubic feet (1.5×109 m3) deposit of helium was found in Tanzania in 2016. 
A large-scale helium plant was opened in Ningxia, China in 2020.

In the United States, most helium is extracted from natural gas of the Hugoton and nearby gas fields in Kansas, Oklahoma, and the Panhandle Field in Texas. 

Much of this gas was once sent by pipeline to the National Helium Reserve, but since 2005 this reserve is being depleted and sold off, and is expected to be largely depleted by 2021, under the October 2013 Responsible Helium Administration and Stewardship Act.

Diffusion of crude natural gas through special semipermeable membranes and other barriers is another method to recover and purify helium. 
In 1996, the U.S. had proven helium reserves, in such gas well complexes, of about 147 billion standard cubic feet (4.2 billion SCM). 

At rates of use at that time (72 million SCM per year in the U.S.; see pie chart below) this would have been enough helium for about 58 years of U.S. use, and less than this (perhaps 80% of the time) at world use rates, although factors in saving and processing impact effective reserve numbers.

Helium must be extracted from natural gas because Helium is present in air at only a fraction of that of neon, yet the demand for Helium is far higher. 
Heliumis estimated that if all neon production were retooled to save helium, 0.1% of the world's helium demands would be satisfied. 

Similarly, only 1% of the world's helium demands could be satisfied by re-tooling all air distillation plants.
Helium can be synthesized by bombardment of lithium or boron with high-velocity protons, or by bombardment of lithium with deuterons, but these processes are a completely uneconomical method of production.

-Liquid helium is used in cryogenics (Helium's largest single use, absorbing about a quarter of production), and in the cooling of superconducting magnets, with Helium's main commercial application in MRI scanners. 
-While balloons are perhaps the best known use of helium, they are a minor part of all helium use. 

-Helium's other industrial uses—as a pressurizing and purge gas, as a protective atmosphere for arc welding, and in processes such as growing crystals to make silicon wafers—account for half of the gas produced. 
-A well-known but minor use is as a lifting gas in balloons and airships.

-In scientific research, the behavior of the two fluid phases of helium-4 (helium I and helium II) is important to researchers studying quantum mechanics (in particular the property of superfluidity) and to those looking at the phenomena, such as superconductivity, produced in matter near absolute zero.

-Helium is used as a cooling medium for the Large Hadron Collider (LHC), and the superconducting magnets in MRI scanners and NMR spectrometers. 
-Helium is also used to keep satellite instruments cool and was used to cool the liquid oxygen and hydrogen that powered the Apollo space vehicles.

-Because of Helium's low density helium is often used to fill decorative balloons, weather balloons and airships. 
Hydrogen was once used to fill balloons.
-Because Helium is very unreactive, helium is used to provide an inert protective atmosphere for making fibre optics and semiconductors, and for arc welding. 

-Helium is also used to detect leaks, such as in car air-conditioning systems, and because Helium diffuses quickly it is used to inflate car air.
-Helium is used for many purposes that require some of Helium's unique properties, such as Helium's low boiling point, low density, low solubility, high thermal conductivity, or inertness. 

-Of the 2014 world helium total production of about 32 million kg (180 million standard cubic meters) helium per year, the largest use (about 32% of the total in 2014) is in cryogenic applications, most of which involves cooling the superconducting magnets in medical MRI scanners and NMR spectrometers. 

-Controlled atmospheres:
Helium is used as a protective gas in growing silicon and germanium crystals, in titanium and zirconium production, and in gas chromatography, because Helium is inert. 
Because of Helium's inertness, thermally and calorically perfect nature, high speed of sound, and high value of the heat capacity ratio, Helium is also useful in supersonic wind tunnels and impulse facilities.

-Gas tungsten arc welding:
Helium is used as a shielding gas in arc welding processes on materials that at welding temperatures are contaminated and weakened by air or nitrogen. 
A number of inert shielding gases are used in gas tungsten arc welding, but helium is used instead of cheaper argon especially for welding materials that have higher heat conductivity, like aluminium or copper.

-Minor uses:
One industrial application for helium is leak detection. 
Because helium diffuses through solids three times faster than air, Helium is used as a tracer gas to detect leaks in high-vacuum equipment (such as cryogenic tanks) and high-pressure containers. 

The tested object is placed in a chamber, which is then evacuated and filled with helium. 
The helium that escapes through the leaks is detected by a sensitive device (helium mass spectrometer), even at the leak rates as small as 10−9 mbar·L/s (10−10 Pa·m3/s). 

The measurement procedure is normally automatic and is called helium integral test. 
A simpler procedure is to fill the tested object with helium and to manually search for leaks with a hand-held device.

Helium leaks through cracks should not be confused with gas permeation through a bulk material. 
While helium has documented permeation constants (thus a calculable permeation rate) through glasses, ceramics, and synthetic materials, inert gases such as helium will not permeate most bulk metals.

Because Helium is lighter than air, airships and balloons are inflated with helium for lift. 
While hydrogen gas is more buoyant, and escapes permeating through a membrane at a lower rate, helium has the advantage of being non-flammable, and indeed fire-retardant. 

Another minor use is in rocketry, where helium is used as an ullage medium to displace fuel and oxidizers in storage tanks and to condense hydrogen and oxygen to make rocket fuel. 

Helium is also used to purge fuel and oxidizer from ground support equipment prior to launch and to pre-cool liquid hydrogen in space vehicles. 
For example, the Saturn V rocket used in the Apollo program needed about 370,000 m3 (13 million cubic feet) of helium to launch.

-Minor commercial and recreational uses:
Helium as a breathing gas has no narcotic properties, so helium mixtures such as trimix, heliox and heliair are used for deep diving to reduce the effects of narcosis, which worsen with increasing depth. 

As pressure increases with depth, the density of the breathing gas also increases, and the low molecular weight of helium is found to considerably reduce the effort of breathing by lowering the density of the mixture. 

This reduces the Reynolds number of flow, leading to a reduction of turbulent flow and an increase in laminar flow, which requires less work of breathing. 

-Helium–neon lasers, a type of low-powered gas laser producing a red beam, had various practical applications which included barcode readers and laser pointers, before they were almost universally replaced by cheaper diode lasers.
-For Helium's inertness and high thermal conductivity, neutron transparency, and because Helium does not form radioactive isotopes under reactor conditions, helium is used as a heat-transfer medium in some gas-cooled nuclear reactors.

-Helium, mixed with a heavier gas such as xenon, is useful for thermoacoustic refrigeration due to the resulting high heat capacity ratio and low Prandtl number.
The inertness of helium has environmental advantages over conventional refrigeration systems which contribute to ozone depletion or global warming.

-Helium is also used in some hard disk drives.
-As with any gas whose density differs from that of air, inhaling a small volume of helium temporarily changes the timbre and quality of the human voice.

-Scientific uses:
The use of helium reduces the distorting effects of temperature variations in the space between lenses in some telescopes, due to Helium's extremely low index of refraction. 
This method is especially used in solar telescopes where a vacuum tight telescope tube would be too heavy.

-Helium is a commonly used carrier gas for gas chromatography.
-The age of rocks and minerals that contain uranium and thorium can be estimated by measuring the level of helium with a process known as helium dating.

-Helium at low temperatures is used in cryogenics, and in certain cryogenics applications. 
As examples of applications, liquid helium is used to cool certain metals to the extremely low temperatures required for superconductivity, such as in superconducting magnets for magnetic resonance imaging. 

The Large Hadron Collider at CERN uses 96 metric tons of liquid helium to maintain the temperature at 1.9 K (−271.25 °C; −456.25 °F).
-Other major uses were pressurizing and purging systems, welding, maintenance of controlled atmospheres, and leak detection. Other uses by category were relatively minor fractions.

-Helium is used as a cooling medium for the Large Hadron Collider (LHC), and the superconducting magnets in MRI scanners and NMR spectrometers. 
Helium is also used to keep satellite instruments cool and was used to cool the liquid oxygen and hydrogen that powered the Apollo space vehicles.

-Because of Helium's low density helium is often used to fill decorative balloons, weather balloons and airships.
-Because Helium is very unreactive, helium is used to provide an inert protective atmosphere for making fibre optics and semiconductors, and for arc welding. 

-Helium is also used to detect leaks, such as in car air-conditioning systems, and because Helium diffuses quickly Helium is used to inflate car airbags after impact.
-Medical uses:
Helium was approved for medical use in the United States in April 2020 for humans and animals.

-A mixture of 80% helium and 20% oxygen is used as an artificial atmosphere for deep-sea divers and others working under pressurised conditions.
-Helium-neon gas lasers are used to scan barcodes in supermarket checkouts. 
A new use for helium is a helium-ion microscope that gives better image resolution than a scanning electron microscope.

-Helium's the most widely used of the inert gases, utilized in arc welding, diving, growing silicon crystals, and as a coolant in MRI (magnetic resonance imaging) scanners.
-Helium-3 can also be used for detecting neutrons from afar. 
This can be useful for catching smugglers illegally trafficking radioactive materials. 

-Helium is also used in certain types of medical lung imaging and has been proposed as a fuel candidate for nuclear fusion.
-Welding Shielding Gas mixtures containing helium. 
-Medical Gas Cylinders supplied as breathing mixtures only by credentialed facilities.

-For Superconducting Magnets in MRIs and NMRs, liquid phase product delivers the lowest possible cryogenic temperatures.
-Special Applications are diverse: breathing air mixtures, cooling of extruded fiber optics, closed-system leak detection, weather balloons, and many more.

-With a boiling point of merely 4 degrees Kelvin above absolute zero, liquid helium is used to cool everything from new materials in research labs to superconducting magnets in MRI scanners. 
In fact, this is the largest single use of helium today, accounting for about one-quarter of all production.

-Used laser applications.
-Helium performs such diverse tasks as cooling the superconducting magnets in MRI scanners, aiding the manufacture of semiconductor chips and finding leaks in ships. 

-Helium has many unique properties: low boiling point, low density, low solubility, high thermal conductivity and inertness, so Helium is use for any application which can explioit these properties. 
-Helium was the first gas used for filling balloons and dirigibles. 
This application goes on in altitude research and for meteorological balloons. 

-Helium is the only cooler which is capable of reaching temperatures lower than 15 K (-434ºF). 
The main application of ultralow temperature is in the development of the superconductivity state, in which the resistance to the electricity flux is almost zero. 

-Other applications are Helium's use as pressurizing gas in liquid propellants for rockets, in helium-oxygen mixtures for divers, as working fluid in nuclear reactors cooled down by gas and as gas carrier in chemical analysis by gas chromatography.

Helium is also used as airbag inflating gas in high pressure capsules.
-The main use of helium is as an inert protection gas in autogenous welding. 
-Helium's biggest potential is found in applications at very low temperatures. 

-Calibration Gas:
Helium is used as a calibration gas and a balance gas in calibration mixtures. 
Helium is also used as carrier gas in gas chromatography. 
Helium is used as a purge gas and a zero (span) gas for analytical instruments.

Liquid helium is used to cool the superconductive magnets in NMR (Nuclear Magnetic Resonance) for analytical or medical purposes and in the R&D to study processes around absolute Zero.

-Nuclear Reaction:
Helium is used for cooling of uranium rods in nuclear reactors.
-Fiber Optic:
Helium is used as a combined cooling and shielding medium for the pulling of optical fibres.

Helium is used as a carrier gas or as a purge gas for a variety of semiconductor processes. 
Helium is also used for epitaxial crystal growth (inert atmosphere).

-Tunnel Work:
Helium is used as a propellant in the "helium cannon" used in model firing tunnels. 
Helium also finds use as a working gas in some hypersonic wind tunnels.

-Atmospheric Research:
Helium is used to fill large balloons for upper atmosphere and cosmic ray studies. 
Small helium balloons are used by weather forecasters to carry meteorological instruments.

-Heat Treatment:
Helium is also used for vacuum breaking in heat treatment furnaces.
-Helium also combines with oxygen to create breathing gas mixtures for divers. 

-With the lowest boiling point of any gas (4.2 Kelvin or –269° Celsius), liquid helium is the coldest matter on Earth. 
This makes it ideal as a cryogenic agent for a number of cutting-edge medical and physics applications. 
For instance, Helium is used to cool superconductive magnetic coils in magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR) medical equipment.

-In fact, helium is indispensable across a wide range of industries. 
For example, Helium is used to pressurise rocket fuel; create inert atmospheres for welding, heat treatment and epitaxial crystal growth; purge semiconductor atmospheres; calibrate analytical instruments; inflate airplane tyres and airbags; test for leaks; inflate large balloons for meteorological studies; and fill electronic tubes in neon signs.

-The non-flammable, low-density properties of helium make Helium a safe choice for the entertainment industry, where Helium is used to inflate balloons at parties and special events.
-The inert gas for your cryogenic, heat transfer, shielding, leak detection, analytical and lifting applications.

-Gaseous helium is used as an inert shielding gas in metal arc and laser welding. 
Helium is also used as a coolant to transfer heat effectively, thanks to its high thermal conductivity,  in the fibre optics and electronics industries. 

-Being both lighter than air and non-flammable, helium is used to inflate both balloons and airships.
-The extremely low temperature of liquid helium is used to maintain the superconducting properties of magnets in applications such as Magnetic Resonance Imagery (MRI), Nuclear Magnetic Resonance (NMR) spectroscopy, and particle physics research. 

-Helium is used as an inert-gas atmosphere for welding metals such as aluminum; in rocket propulsion (to pressurize fuel tanks, especially those for liquid hydrogen, because only helium is still a gas at liquid-hydrogen temperature); in meteorology (as a lifting gas for instrument-carrying balloons); in cryogenics (as a coolant because liquid helium is the coldest substance); and in high-pressure breathing operations (mixed with oxygen, as in scuba diving and caisson work, especially because of its low solubility in the bloodstream). 

-Helium serves as a carrier gas for gas chromatography (GC) in analytical laboratories and as a leak detection gas in a wide range of industries. 
-Meteorites and rocks have been analyzed for helium content as a means of dating.

-Helium is inert and the least soluble of all gases in liquids and is therefore used as a pressurization. 
-Being inert, helium is used as a constituent in neutral atmospheres e.g., in heat treatment applications requiring a protective atmosphere.

-Helium is used extensively in the welding industry as an inert shielding gas for arc welding. 
-Helium is also used in conjunction with helium (“leak”) detectors to test the integrity of fabricated components and systems.

After an oil drilling operation in 1903 in Dexter, Kansas produced a gas geyser that would not burn, Kansas state geologist Erasmus Haworth collected samples of the escaping gas and took them back to the University of Kansas at Lawrence where, with the help of chemists Hamilton Cady and David McFarland, he discovered that the gas consisted of, by volume, 72% nitrogen, 15% methane (a combustible percentage only with sufficient oxygen), 1% hydrogen, and 12% an unidentifiable gas. 

With further analysis, Cady and McFarland discovered that 1.84% of the gas sample was helium. 
This showed that despite its overall rarity on Earth, helium was concentrated in large quantities under the American Great Plains, available for extraction as a byproduct of natural gas.

This enabled the United States to become the world's leading supplier of helium. 
Following a suggestion by Sir Richard Threlfall, the United States Navy sponsored three small experimental helium plants during World War I. 

The goal was to supply barrage balloons with the non-flammable, lighter-than-air gas. 
A total of 5,700 m3 (200,000 cu ft) of 92% helium was produced in the program even though less than a cubic meter of the gas had previously been obtained. 

Some of Helium was used in the world's first helium-filled airship, the U.S. Navy's C-class blimp C-7, which flew Helium's maiden voyage from Hampton Roads, Virginia, to Bolling Field in Washington, D.C., on December 1, 1921, nearly two years before the Navy's first rigid helium-filled airship, the Naval Aircraft Factory-built USS Shenandoah, flew in September 1923.

Although the extraction process using low-temperature gas liquefaction was not developed in time to be significant during World War I, production continued. 
Helium was primarily used as a lifting gas in lighter-than-air craft. 

During World War II, the demand increased for helium for lifting gas and for shielded arc welding. 
The helium mass spectrometer was also vital in the atomic bomb Manhattan Project.

The government of the United States set up the National Helium Reserve in 1925 at Amarillo, Texas, with the goal of supplying military airships in time of war and commercial airships in peacetime. 

Because of the Helium Act of 1925, which banned the export of scarce helium on which the US then had a production monopoly, together with the prohibitive cost of the gas, the Hindenburg, like all German Zeppelins, was forced to use hydrogen as the lift gas. 

The helium market after World War II was depressed but the reserve was expanded in the 1950s to ensure a supply of liquid helium as a coolant to create oxygen/hydrogen rocket fuel (among other uses) during the Space Race and Cold War. 
Helium use in the United States in 1965 was more than eight times the peak wartime consumption.

After the "Helium Acts Amendments of 1960" (Public Law 86–777), the U.S. Bureau of Mines arranged for five private plants to recover helium from natural gas. 

For this helium conservation program, the Bureau built a 425-mile (684 km) pipeline from Bushton, Kansas, to connect those plants with the government's partially depleted Cliffside gas field near Amarillo, Texas. 

This helium-nitrogen mixture was injected and stored in the Cliffside gas field until needed, at which time Helium was further purified.

By 1995, a billion cubic meters of the gas had been collected and the reserve was US$1.4 billion in debt, prompting the Congress of the United States in 1996 to phase out the reserve. 

The resulting Helium Privatization Act of 1996(Public Law 104–273) directed the United States Department of the Interior to empty the reserve, with sales starting by 2005.

Helium produced between 1930 and 1945 was about 98.3% pure (2% nitrogen), which was adequate for airships. 
In 1945, a small amount of 99.9% helium was produced for welding use. 
By 1949, commercial quantities of Grade A 99.95% helium were available.

For many years, the United States produced more than 90% of commercially usable helium in the world, while extraction plants in Canada, Poland, Russia, and other nations produced the remainder. 

In the mid-1990s, a new plant in Arzew, Algeria, producing 17 million cubic meters (600 million cubic feet) began operation, with enough production to cover all of Europe's demand. 

Meanwhile, by 2000, the consumption of helium within the U.S. had risen to more than 15 million kg per year. In 2004–2006, additional plants in Ras Laffan, Qatar, and Skikda, Algeria were built. 

Algeria quickly became the second leading producer of helium. 
Through this time, both helium consumption and the costs of producing helium increased. 
From 2002 to 2007 helium prices doubled.

As of 2012, the United States National Helium Reserve accounted for 30 percent of the world's helium. 
The reserve was expected to run out of helium in 2018. 

Despite that, a proposed bill in the United States Senate would allow the reserve to continue to sell the gas. 
Other large reserves were in the Hugoton in Kansas, United States, and nearby gas fields of Kansas and the panhandles of Texas and Oklahoma. 

New helium plants were scheduled to open in 2012 in Qatar, Russia, and the US state of Wyoming, but they were not expected to ease the shortage.

In 2013, Qatar started up the world's largest helium unit, although the 2017 Qatar diplomatic crisis severely affected helium production there. 
2014 was widely acknowledged to be a year of over-supply in the helium business, following years of renowned shortages. 

Nasdaq reported (2015) that for Air Products, an international corporation that sells gases for industrial use, helium volumes remain under economic pressure due to feedstock supply constraints.

Although Helium is rare on Earth, helium is the second most abundant element in the known Universe, constituting 23% of its baryonic mass. 
Only hydrogen is more abundant. 
The vast majority of helium was formed by Big Bang nucleosynthesis one to three minutes after the Big Bang. 

As such, measurements of Helium's abundance contribute to cosmological models. 
In stars, Helium is formed by the nuclear fusion of hydrogen in proton–proton chain reactions and the CNO cycle, part of stellar nucleosynthesis.

In the Earth's atmosphere, the concentration of helium by volume is only 5.2 parts per million. 
The concentration is low and fairly constant despite the continuous production of new helium because most helium in the 
Earth's atmosphere escapes into space by several processes. 
In the Earth's heterosphere, a part of the upper atmosphere, helium and other lighter gases are the most abundant elements.

Most helium on Earth is a result of radioactive decay. 
Helium is found in large amounts in minerals of uranium and thorium, including uraninite and its varieties cleveite and pitchblende, carnotite and monazite (a group name; "monazite" usually refers to monazite-(Ce)), because they emit alpha particles (helium nuclei, He2+) to which electrons immediately combine as soon as the particle is stopped by the rock. 

In this way an estimated 3000 metric tons of helium are generated per year throughout the lithosphere. 
In the Earth's crust, the concentration of helium is 8 parts per billion. 

In seawater, the concentration is only 4 parts per trillion. 
There are also small amounts in mineral springs, volcanic gas, and meteoric iron. 

Because helium is trapped in the subsurface under conditions that also trap natural gas, the greatest natural concentrations of helium on the planet are found in natural gas, from which most commercial helium is extracted. 
The concentration varies in a broad range from a few ppm to more than 7% in a small gas field in San Juan County, New Mexico.

As of 2021 the world's helium reserves were estimated at 31 billion cubic meters, with a third of that being in Qatar.
In 2015 and 2016 additional probable reserves were announced to be under the Rocky Mountains in North America and in the East African Rift.

For large-scale use, helium is extracted by fractional distillation from natural gas, which can contain as much as 7% helium. 
Since helium has a lower boiling point than any other element, low temperature and high pressure are used to liquefy nearly all the other gases (mostly nitrogen and methane). 

The resulting crude helium gas is purified by successive exposures to lowering temperatures, in which almost all of the remaining nitrogen and other gases are precipitated out of the gaseous mixture. 
Activated charcoal is used as a final purification step, usually resulting in 99.995% pure Grade-A helium. 

The principal impurity in Grade-A helium is neon. 
In a final production step, most of the helium that is produced is liquefied via a cryogenic process. 

This is necessary for applications requiring liquid helium and also allows helium suppliers to reduce the cost of long-distance transportation, as the largest liquid helium containers have more than five times the capacity of the largest gaseous helium tube trailers.

Helium is commercially available in either liquid or gaseous form. As a liquid, it can be supplied in small insulated containers called dewars which hold as much as 1,000 liters of helium, or in large ISO containers which have nominal capacities as large as 42 m3 (around 11,000 U.S. gallons). 

In gaseous form, small quantities of helium are supplied in high-pressure cylinders holding as much as 8 m3 (approx. 282 standard cubic feet), while large quantities of high-pressure gas are supplied in tube trailers which have capacities of as much as 4,860 m3 (approx. 172,000 standard cubic feet).

Although helium was now potentially available in large quantities, it remained a laboratory curiosity for almost 10 years, and the entire American supply rested in three glass tubes, dusty and almost forgotten on the shelf in Bailey Hall at The University of Kansas. 

When Clifford W. Siebel came to Kansas to work on an advanced degree, Cady suggested that he should re-examine the helium content in natural gas for his thesis research. 

Siebel approached the problem reluctantly and without enthusiasm. 
When he read his results before a scientific audience in Kansas City in 1917, he concluded by expressing regret "that the work did not have a practical application." 

A representative from the U.S. Bureau of Mines "took immediate issue with that remark, and ... read a part of a letter from [Sir] William Ramsay in England in which the suggestion was made that the United States produce enough helium to inflate lighter-than-air craft for the Allies." 

The nonflammable and unreactive helium was desirable because it had almost the same lifting power as gaseous hydrogen, which is dangerous to handle because it is flammable.

Siebel was selling meager quantities of helium for $2,500 per cubic foot. He quickly calculated that at that rate, the cost of filling a small blimp was more than $100 million. 

Ten years later, after the U.S. government established plants at Fort Worth and Amarillo, Texas, the cost had dropped to three cents per cubic foot. 

Large-scale production of helium came too late to be of much value in World War I, but it did play a major role in World War II, when helium-filled U.S. 

Navy patrol blimps safely escorted thousands of ships carrying troops and supplies. 
The blimps used sensitive listening devices that when lowered into the water could detect submarines up to five miles away. 

At the time, the Allies had a virtual monopoly on helium, because the only known gas wells capable of producing helium in large quantities were in the United States and Canada.

Once helium became readily available in large quantities, other uses quickly followed. 
Today the U.S. Bureau of Land Management manages helium gas reserves, leasing, and storage. 

According to the bureau, "helium plays a prominent role in the Government's space, defense, and energy programs, such as pressurization of liquid propellants used by the space shuttle, weapons development, and nuclear fusion reactor experiments. 

Liquid helium uses include cooling infrared detectors, space simulations, materials testing, and biological and superconductivity research. 

Gaseous helium uses include various lighter-than-air activities, helium-neon lasers, detecting gas leaks, helium-oxygen mixture for deep sea diving, and high-speed welding of special metals." 

Helium has also been used for producing extremely high velocities in wind tunnels and in hospitals Helium serves as a cryogenic liquid for magnetic resonance imaging. 
Helium is still considered a strategic reserve material.

Helium constitutes about 23 percent of the mass of the universe and is thus second in abundance to hydrogen in the cosmos. Helium is concentrated in stars, where it is synthesized from hydrogen by nuclear fusion. 

Although helium occurs in Earth’s atmosphere only to the extent of 1 part in 200,000 (0.0005 percent) and small amounts occur in radioactive minerals, meteoric iron, and mineral springs, great volumes of helium are found as a component (up to 7.6 percent) in natural gases in the United States (especially in Texas, New Mexico, Kansas, Oklahoma, Arizona, and Utah). 

Smaller supplies have been discovered in Algeria, Australia, Poland, Qatar, and Russia. 
Ordinary air contains about 5 parts per million of helium, and Earth’s crust is only about 8 parts per billion.

The nucleus of every helium atom contains two protons, but, as is the case with all elements, isotopes of helium exist. 
The known isotopes of helium contain from one to six neutrons, so their mass numbers range from three to eight. 

Of these six isotopes, only those with mass numbers of three (helium-3, or 3He) and four (helium-4, or 4He) are stable; all the others are radioactive, decaying very rapidly into other substances. 

The helium that is present on Earth is not a primordial component but has been generated by radioactive decay. 
Alpha particles, ejected from the nuclei of heavier radioactive substances, are nuclei of the isotope helium-4. 

Helium does not accumulate in large quantities in the atmosphere because Earth’s gravity is not sufficient to prevent its gradual escape into space. 

The trace of the isotope helium-3 on Earth is attributable to the negative beta decay of the rare hydrogen-3 isotope (tritium). 

Helium-4 is by far the most plentiful of the stable isotopes: helium-4 atoms outnumber those of helium-3 about 700,000:1 in atmospheric helium and about 7,000,000:1 in certain helium-bearing minerals.

In the perspective of quantum mechanics, helium is the second simplest atom to model, following the hydrogen atom. 
Helium is composed of two electrons in atomic orbitals surrounding a nucleus containing two protons and (usually) two neutrons. 

As in Newtonian mechanics, no system that consists of more than two particles can be solved with an exact analytical mathematical approach (see 3-body problem) and helium is no exception. 

Thus, numerical mathematical methods are required, even to solve the system of one nucleus and two electrons.
Such computational chemistry methods have been used to create a quantum mechanical picture of helium electron binding which is accurate to within < 2% of the correct value, in a few computational steps. 

Such models show that each electron in helium partly screens the nucleus from the other, so that the effective nuclear charge Z which each electron sees, is about 1.69 units, not the 2 charges of a classic "bare" helium nucleus.

Related stability of the helium-4 nucleus and electron shell
The nucleus of the helium-4 atom is identical with an alpha particle. 

High-energy electron-scattering experiments show its charge to decrease exponentially from a maximum at a central point, exactly as does the charge density of helium's own electron cloud. 

This symmetry reflects similar underlying physics: the pair of neutrons and the pair of protons in helium's nucleus obey the same quantum mechanical rules as do helium's pair of electrons (although the nuclear particles are subject to a different nuclear binding potential), so that all these fermions fully occupy 1s orbitals in pairs, none of them possessing orbital angular momentum, and each cancelling the other's intrinsic spin. 

Adding another of any of these particles would require angular momentum and would release substantially less energy (in fact, no nucleus with five nucleons is stable). 

This arrangement is thus energetically extremely stable for all these particles, and this stability accounts for many crucial facts regarding helium in nature.

For example, the stability and low energy of the electron cloud state in helium accounts for the element's chemical inertness, and also the lack of interaction of helium atoms with each other, producing the lowest melting and boiling points of all the elements.

In a similar way, the particular energetic stability of the helium-4 nucleus, produced by similar effects, accounts for the ease of helium-4 production in atomic reactions that involve either heavy-particle emission or fusion. 

Some stable helium-3 (2 protons and 1 neutron) is produced in fusion reactions from hydrogen, but it is a very small fraction compared to the highly favorable helium-4.

The unusual stability of the helium-4 nucleus is also important cosmologically: it explains the fact that in the first few minutes after the Big Bang, as the "soup" of free protons and neutrons which had initially been created in about 6:1 ratio cooled to the point that nuclear binding was possible, almost all first compound atomic nuclei to form were helium-4 nuclei. 

So tight was helium-4 binding that helium-4 production consumed nearly all of the free neutrons in a few minutes, before they could beta-decay, and also leaving few to form heavier atoms such as lithium, beryllium, or boron. 

Helium-4 nuclear binding per nucleon is stronger than in any of these elements (see nucleogenesis and binding energy) and thus, once helium had been formed, no energetic drive was available to make elements 3, 4 and 5. 

It was barely energetically favorable for helium to fuse into the next element with a lower energy per nucleon, carbon. 
However, due to lack of intermediate elements, this process requires three helium nuclei striking each other nearly simultaneously. 

There was thus no time for significant carbon to be formed in the few minutes after the Big Bang, before the early expanding universe cooled to the temperature and pressure point where helium fusion to carbon was no longer possible. 

This left the early universe with a very similar ratio of hydrogen/helium as is observed today (3 parts hydrogen to 1 part helium-4 by mass), with nearly all the neutrons in the universe trapped in helium-4.

All heavier elements (including those necessary for rocky planets like the Earth, and for carbon-based or other life) have thus been created since the Big Bang in stars which were hot enough to fuse helium itself. 

All elements other than hydrogen and helium today account for only 2% of the mass of atomic matter in the universe. 
Helium-4, by contrast, makes up about 23% of the universe's ordinary matter—nearly all the ordinary matter that is not hydrogen.

Helium is the second least reactive noble gas after neon, and thus the second least reactive of all elements. 
Helium is chemically inert and monatomic in all standard conditions. 

Because of helium's relatively low molar (atomic) mass, Helium's thermal conductivity, specific heat, and sound speed in the gas phase are all greater than any other gas except hydrogen. 

For these reasons and the small size of helium monatomic molecules, helium diffuses through solids at a rate three times that of air and around 65% that of hydrogen.

Helium is the least water-soluble monatomic gas, and one of the least water-soluble of any gas (CF4, SF6, and C4F8 have lower mole fraction solubilities: 0.3802, 0.4394, and 0.2372 x2/10−5, respectively, versus helium's 0.70797 x2/10−5), and helium's index of refraction is closer to unity than that of any other gas. 

Helium has a negative Joule–Thomson coefficient at normal ambient temperatures, meaning Helium heats up when allowed to freely expand. 

Only below Helium's Joule–Thomson inversion temperature (of about 32 to 50 K at 1 atmosphere) does Helium cool upon free expansion. 
Once precooled below this temperature, helium can be liquefied through expansion cooling.

Most extraterrestrial helium is found in a plasma state, with properties quite different from those of atomic helium. 
In a plasma, helium's electrons are not bound to Helium's nucleus, resulting in very high electrical conductivity, even when the gas is only partially ionized. 

The charged particles are highly influenced by magnetic and electric fields. 
For example, in the solar wind together with ionized hydrogen, the particles interact with the Earth's magnetosphere, giving rise to Birkeland currents and the aurora.

Unlike any other element, helium will remain liquid down to absolute zero at normal pressures. 
This is a direct effect of quantum mechanics: specifically, the zero point energy of the system is too high to allow freezing. 

Solid helium requires a temperature of 1–1.5 K (about −272 °C or −457 °F) at about 25 bar (2.5 MPa) of pressure. 
Helium is often hard to distinguish solid from liquid helium since the refractive index of the two phases are nearly the same. 

The solid Helium has a sharp melting point and has a crystalline structure, but Heliumis highly compressible; applying pressure in a laboratory can decrease its volume by more than 30%. 

With a bulk modulus of about 27 MPa it is ~100 times more compressible than water. 
Solid helium has a density of 0.214±0.006 g/cm3 at 1.15 K and 66 atm; the projected density at 0 K and 25 bar (2.5 MPa) is 0.187±0.009 g/cm3. 

At higher temperatures, helium will solidify with sufficient pressure. 
At room temperature, this requires about 114,000 atm.

Why would such a valuable resource be squandered? 
Basically, Helium's because the price of helium does not reflect its value. 

Most of the world's supply of helium is held by the United States National Helium Reserve, which was mandated to sell off all of Helium's stockpile by 2015, regardless of price. 

This was based on a 1996 law, the Helium Privatization Act, which was intended to help the government recoup the cost of building up the reserve. 

Though the uses of helium multiplied, the law had not been revisited, so by 2013 much of the planet's stockpile of helium was sold at an extremely low price.

In 2013, the U.S. Congress did re-examine the law, ultimately passing a bill, the Helium Stewardship Act, aimed at maintaining the helium reserves.

Recent research indicates there's more helium, particularly in groundwater, than scientists previously estimated. 
Also, although the process is extremely slow, ongoing radioactive decay of natural uranium and other radioisotopes does generate additional helium. 

That's the good news. 
The bad news is that it will require more money and new technology to recover the element. 

The other bad news is that there isn't going to be helium that we can get from the planets near us because those planets also exert too little gravity to hold the gas. 
Perhaps at some point, we may find a way to "mine" the element from gas giants further out in the solar system.

If helium is so lightweight that it escapes Earth's gravity, you may be wondering about whether we may run out of hydrogen. 
Even though hydrogen forms chemical bonds with itself to make H2 gas, it's still lighter than even one helium atom. 

The reason we will not run out is that hydrogen forms bonds with other atoms besides itself. 
The element is bound into water molecules and organic compounds. 

Helium, on the other hand, is a noble gas with a stable electron shell structure. 
Since Helium doesn't form chemical bonds, Helium isn't preserved in compounds.

Far from the great scientific centers of Europe, a jubilant crowd gathered in the small town of Dexter, Kansas, in May 1903. 
Situated in the vast Great Plains, Dexter was pinning its hopes for economic prosperity on a newly drilled well that had unleashed "a howling gasser." 

As nine million cubic feet of gas escaped each day before the equipment could be found to cap the well, the drilling company wasted no time in selling stock and planning for additional wells. 

The citizens of Dexter envisioned new industries such as ore smelters and brick and glass plants coming to their little town. 
To celebrate their good fortune, the people of Dexter planned a huge celebration, complete with band music, patriotic speeches, and games. 

The lighting of the escaping gas was planned as the spectacular climax to the day's events. 
Promotional circulars promised that "a great pillar of flame from the burning well will light the entire countryside for a day and a night."

After an appropriately exhilarating address by the mayor, the excited gathering watched with anticipation as a burning bale of hay was slowly moved into contact with the gusher. 
Instead of the expected conflagration, however, the flames of the burning bale were quickly extinguished.

Undaunted, the mayor repeated the process several times, but with the same results. 
Disappointed and puzzled, the crowd slowly dispersed, calling this strange emanation from the well "wind gas." 
Others said it was a well of "hot air." Understandably, the company "did not wish that it be given great publicity."

Dismay over the gas well's failure spread throughout Dexter, but Erasmus Haworth, the official state geologist, was intrigued by this unusual event. 

Haworth, a geology faculty member at The University of Kansas in Lawrence, arranged for a large steel cylinder to be filled with the Dexter gas. 

Upon his return to Lawrence, Haworth discussed the gas with chemistry professor David F. McFarland, who began a routine analysis of the cylinder's contents. 
The results readily gave a scientific explanation to the Dexter puzzle. 

The gas contained only 15% combustible methane, which would not burn in the presence of almost 72% nonflammable nitrogen. 
Haworth and McFarland reported their results to a Geological Society of America meeting in Philadelphia on Dec. 30, 1904. 

They revealed that the Dexter gas also contained 12% of an "inert residue" and promised that the investigation of this residue would "be carried out as soon as time would permit."

Today, we honor helium, that most noble of gasses, which was discovered 150 years ago. 
You may know the second element on the periodic table as the stuff that fills party balloons and makes your voice sound like Alvin the Chipmunk, but it's not all fun and games for the colorless, odorless gas. 
Helium is a workhorse for the science and technology industries. 

Despite its many earthbound uses, helium is actually named after the Greek Titan of the sun -- Helios. 
That's because the first evidence of its existence was discovered in sunlight. 

During a solar eclipse in India on August 18, 1868, French scientist Jules Janssen observed the sun's atmosphere through an instrument that separated the colors of light into a spectrum. 

He later realized he could observe even without an eclipse, and he found a mysterious yellow line in the data. 
Working separately, English scientist Norman Lockyer also observed the bright yellow line a few months later. 

It was Lockyer who proposed that the mysterious line was evidence of a new element, which he and chemist Edward Frankland christened helium.

It took another 27 years before helium was discovered on Earth inside a mineral called cleveite. 
As often happens in science, the discovery was again made around the same time by multiple people, in this case Scottish chemist William Ramsay and Swedish chemists Per Teodor Cleve and Nils Abraham Langlet.

In the ensuing 123 years, scientists and hobbyists alike have continued to explore and exploit the unique properties of this important element.

The first evidence of helium was observed on August 18, 1868, as a bright yellow line with a wavelength of 587.49 nanometers in the spectrum of the chromosphere of the Sun. 
The line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur, India. 

This line was initially assumed to be sodium. On October 20 of the same year, English astronomer, Norman Lockyer, observed a yellow line in the solar spectrum, which, he named the D3 because Helium was near the known D1 and D2 Fraunhofer line lines of sodium. 

He concluded that it was caused by an element in the Sun unknown on Earth. Lockyer and English chemist Edward Frankland named the element with the Greek word for the Sun, ἥλιος (helios).

In 1881, Italian physicist Luigi Palmieri detected helium on Earth for the first time through its D3 spectral line, when he analyzed a material that had been sublimated during a recent eruption of Mount Vesuvius.

On March 26, 1895, Scottish chemist Sir William Ramsay isolated helium on Earth by treating the mineral cleveite (a variety of uraninite with at least 10% rare-earth elements) with mineral acids. 

Ramsay was looking for argon but, after separating nitrogen and oxygen from the gas, liberated by sulfuric acid, he noticed a bright yellow line that matched the D3 line observed in the spectrum of the Sun. 

These samples were identified as helium by Lockyer and British physicist William Crookes. 
Helium was independently isolated from cleveite, in the same year, by chemists, Per Teodor Cleve and Abraham Langlet, in Uppsala, Sweden, who collected enough of the gas to accurately determine its atomic weight. 

Helium was also isolated by the American geochemist, William Francis Hillebrand, prior to Ramsay's discovery, when he noticed unusual spectral lines while testing a sample of the mineral uraninite. 

Hillebrand, however, attributed the lines to nitrogen. 
His letter of congratulations to Ramsay offers an interesting case of discovery, and near-discovery, in science.

In 1907, Ernest Rutherford and Thomas Royds demonstrated that alpha particles are helium nuclei, by allowing the particles to penetrate the thin, glass wall of an evacuated tube, then creating a discharge in the tube, to study the spectrum of the new gas inside. 

In 1908, helium was first liquefied by Dutch physicist Heike Kamerlingh Onnes by cooling the gas to less than 5 K (−268.15 °C; −450.67 °F). 
He tried to solidify it, by further reducing the temperature, but failed, because helium does not solidify at atmospheric pressure. 

Onnes' student Willem Hendrik Keesom was eventually able to solidify 1 cm3 of helium in 1926 by applying additional external pressure.

In 1913, Niels Bohr published his "trilogy" on atomic structure that included a reconsideration of the Pickering–Fowler series as central evidence in support of his model of the atom. 

This series is named for Edward Charles Pickering, who in 1896 published observations of previously unknown lines in the spectrum of the star ζ Puppis (these are now known to occur with Wolf–Rayet and other hot stars). 

Pickering attributed the observation (lines at 4551, 5411, and 10123 Å) to a new form of hydrogen with half-integer transition levels. 

In 1912, Alfred Fowler managed to produce similar lines from a hydrogen-helium mixture, and supported Pickering's conclusion as to their origin. 

Bohr's model does not allow for half-integer transitions (nor does quantum mechanics) and Bohr concluded that Pickering and Fowler were wrong, and instead assigned these spectral lines to ionised helium, He+. 

Fowler was initially skeptical but was ultimately convinced that Bohr was correct, and by 1915 "spectroscopists had transferred [the Pickering–Fowler series] definitively [from hydrogen] to helium.

" Bohr's theoretical work on the Pickering series had demonstrated the need for "a re-examination of problems that seemed already to have been solved within classical theories" and provided important confirmation for his atomic theory.

In 1938, Russian physicist Pyotr Leonidovich Kapitsa discovered that helium-4 has almost no viscosity at temperatures near absolute zero, a phenomenon now called superfluidity. 

This phenomenon is related to Bose–Einstein condensation. 
In 1972, the same phenomenon was observed in helium-3, but at temperatures much closer to absolute zero, by American physicists Douglas D. Osheroff, David M. Lee, and Robert C. Richardson. 

The phenomenon in helium-3 is thought to be related to pairing of helium-3 fermions to make bosons, in analogy to Cooper pairs of electrons producing superconductivity.

Helium was discovered in the gaseous atmosphere surrounding the Sun by the French astronomer Pierre Janssen, who detected a bright yellow line in the spectrum of the solar chromosphere during an eclipse in 1868; this line was initially assumed to represent the element sodium. 

That same year the English astronomer Joseph Norman Lockyer observed a yellow line in the solar spectrum that did not correspond to the known D1 and D2 lines of sodium, and so he named it the D3 line. 

Lockyer concluded that the D3 line was caused by an element in the Sun that was unknown on Earth; he and the chemist Edward Frankland used the Greek word for sun, hēlios, in naming the element. 
The British chemist Sir William Ramsay discovered the existence of helium on Earth in 1895. 

Ramsay obtained a sample of the uranium-bearing mineral cleveite, and, upon investigating the gas produced by heating the sample, he found that a unique bright yellow line in its spectrum matched that of the D3 line observed in the spectrum of the Sun; the new element of helium was thus conclusively identified. 

In 1903 Ramsay and Frederick Soddy further determined that helium is a product of the spontaneous disintegration of radioactive substances.

Helium, the second most abundant element in the universe, was discovered on the sun before it was found on the earth. 
Pierre-Jules-César Janssen, a French astronomer, noticed a yellow line in the sun's spectrum while studying a total solar eclipse in 1868. 

Sir Norman Lockyer, an English astronomer, realized that this line, with a wavelength of 587.49 nanometers, could not be produced by any element known at the time. 

It was hypothesized that a new element on the sun was responsible for this mysterious yellow emission. 
This unknown element was named helium by Lockyer.

The hunt to find helium on earth ended in 1895. 
Sir William Ramsay, a Scottish chemist, conducted an experiment with a mineral containing uranium called clevite. 

He exposed the clevite to mineral acids and collected the gases that were produced. 
He then sent a sample of these gases to two scientists, Lockyer and Sir William Crookes, who were able to identify the helium within it. 

Two Swedish chemists, Nils Langlet and Per Theodor Cleve, independently found helium in clevite at about the same time as Ramsay.

Helium makes up about 0.0005% of the earth's atmosphere. 
This trace amount of helium is not gravitationally bound to the earth and is constantly lost to space. 

The earth's atmospheric helium is replaced by the decay of radioactive elements in the earth's crust. 
Alpha decay, one type of radioactive decay, produces particles called alpha particles. 

An alpha particle can become a helium atom once it captures two electrons from its surroundings. 
This newly formed helium can eventually work its way to the atmosphere through cracks in the crust.

Helium is commercially recovered from natural gas deposits, mostly from Texas, Oklahoma and Kansas. 
Helium gas is used to inflate blimps, scientific balloons and party balloons. 

Helium is used as an inert shield for arc welding, to pressurize the fuel tanks of liquid fueled rockets and in supersonic windtunnels. 

Helium is combined with oxygen to create a nitrogen free atmosphere for deep sea divers so that they will not suffer from a condition known as nitrogen narcosis. 

Liquid helium is an important cryogenic material and is used to study superconductivity and to create superconductive magnets. 

The Department of Energy's Jefferson Lab uses large amounts of liquid helium to operate Helium's superconductive electron accelerator.

Helium is an inert gas and does not easily combine with other elements. 
There are no known compounds that contain helium, although attempts are being made to produce helium diflouride (HeF2).

Molecular Weight: 4.00260    
Hydrogen Bond Donor Count: 0    
Hydrogen Bond Acceptor Count: 0    
Rotatable Bond Count: 0    
Exact Mass: 4.002603254    
Monoisotopic Mass: 4.002603254    
Topological Polar Surface Area: 0 Ų    
Heavy Atom Count: 1    

Formal Charge: 0    
Complexity: 0    
Isotope Atom Count: 0    
Defined Atom Stereocenter Count: 0    
Undefined Atom Stereocenter Count: 0    
Defined Bond Stereocenter Count: 0    
Undefined Bond Stereocenter Count: 0    
Covalently-Bonded Unit Count: 1    
Compound Is Canonicalized: Yes

Atomic number: 2
Atomic mass: 4.00260 g.mol -1
Electronegativity according to Pauling: unknown
Density: 0.178*10 -3 g.cm -3 at 20 °C
Melting point: - 272.2 (26 atm) °C
Boiling point: - 268.9 °C
Vanderwaals radius: 0.118 nm
Ionic radius: unknown

Isotopes: 2
Electronic shell: 1s 2
Energy of first ionisation: 2372 kJ.mol -1
Discovered by: Sir Ramsey in 1895
Name: helium
Symbol: He
Atomic number: 2
Relative atomic mass (Ar): 4.002602 
Standard state: gas at 298 K

Appearance: colourless
Classification: Non-metallic
Group in periodic table: 18
Group name: Noble gas
Period in periodic table: 1
Block in periodic table: p
Shell structure: 2
Appearance Form: Compressed gas

Odour: No data available
Odour Threshold: No data available
pH: No data available
Melting point/freezing point:
Melting point/range: -272,19 °C at 26 hPa
Initial boiling point and boiling range: -268,89 °C at 1.013 hPa
Flash point: Not applicable

Evaporation rate: No data available
Flammability (solid, gas): No data available
Upper/lower flammability or explosive limits: No data available
Vapour pressure: No data available
Vapour density: 0,14 - (Air = 1.0)
Relative density: No data available
Water solubility: 0,0015 g/l

Partition coefficient: n-octanol/water: No data available
Auto-ignition temperature: No data available
Decomposition temperature: No data available
Viscosity: No data available
Explosive properties: No data available
Oxidizing properties: No data available
Other safety information:
Relative vapour density: 0,14 - (Air = 1.0)

-Description of first aid measures:
*General advice:
Consult a physician. 
Show this safety data sheet to the doctor in attendance.

*If inhaled:
If breathed in, move person into fresh air. 
Consult a physician.

*In case of skin contact:
Wash off with soap and plenty of water. 
Consult a physician.

*In case of eye contact:
Flush eyes with water as a precaution.

*If swallowed: 
Rinse mouth with water. 
Consult a physician.

-Indication of any immediate medical attention and special treatment needed:
No data available

-Personal precautions, protective equipment and emergency procedures:
Ensure adequate ventilation. 
Evacuate personnel to safe areas.

-Environmental precautions:
Do not let product enter drains.

-Methods and materials for containment and cleaning up:
Clean up promptly by sweeping or vacuum.

-Extinguishing media:
*Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.

-Further information:
Use water spray to cool unopened containers.

-Control parameters:
--Components with workplace control parameters:
-Exposure controls:
--Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice. 
Wash hands before breaks and at the end of workday.

--Personal protective equipment:
*Eye/face protection:
Use equipment for eye protection.

*Skin protection:
Handle with gloves. 
Wash and dry hands.

-Control of environmental exposure:
Do not let product enter drains.

-Conditions for safe storage, including any incompatibilities:
Store in cool place. 
Keep container tightly closed in a dry and well-ventilated place.
Contents under pressure.

No data available

-Chemical stability:
Stable under recommended storage conditions.

-Possibility of hazardous reactions:
No data available

-Conditions to avoid:
No data available

-Hazardous decomposition products:
Other decomposition products - No data available

Atomic helium
Helium (USP)
Helium [USP]
HSDB 553
helium atom
Helium, compressed
Helium, compressed [UN1046] [Nonflammable gas]
INS NO.939
Helium, >=99.995%
Helium, >=99.999%
Helium, Messer(R) CANGas, 99.999%
E 939
Helium, refrigerated liquid (cryogenic liquid)
Helium, compressed [UN1046] [Nonflammable gas]
Helium, refrigerated liquid (cryogenic liquid) [UN1963] [Nonflammable gas]


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