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Helium

physical science Maturity 11-13 Next article →

Helium is a unique chemical element with the symbol He and atomic number 2. It is a colorless, odorless, and non-toxic gas that is considered chemically inert. This means it does not easily react with other substances. In the periodic table, helium is the first member of the noble gas group. It is the second-lightest element in the observable universe, following only hydrogen.

Helium atom QM
Helium atom QM

Because it is so light, helium is also the second-most abundant element in space. It accounts for approximately 24% of the total elemental mass in the universe. This mass is more than 12 times greater than the mass of all heavier elements combined. This high abundance is seen in both the Sun and the planet Jupiter.

The abundance of helium is driven by its high nuclear binding energy. This energy is specifically related to the helium-4 isotope. This high energy explains why helium-4 is a common product of both nuclear fusion and radioactive decay. Most helium in the universe is helium-4, which was largely formed during the Big Bang. However, stars also create large amounts of new helium. They do this through nuclear fusion, which is the process of joining hydrogen atoms together.

Binding energy curve - common isotopes
Binding energy curve - common isotopes

On Earth, helium is much rarer, making up only about 5.2 parts per million by volume in our atmosphere. Most of our terrestrial helium comes from the radioactive decay of heavy elements like thorium and uranium. As these elements decay, they emit alpha particles, which are actually helium-4 nuclei. This gas often becomes trapped in natural gas reserves deep underground.

The history of helium began with observations of the Sun. During a total solar eclipse on August 18, 1868, astronomers noticed something unusual. French astronomer Jules Janssen detected a bright yellow spectral line in the Sun's chromosphere. A spectral line is a specific signature of light that helps identify elements. At first, many thought this line was just sodium. However, English astronomer Norman Lockyer observed the same yellow line from Britain. He named this signature the D3 line because it was near the known D1 and D2 lines of sodium.

Helium spectrum
Helium spectrum

Lockyer was the first to propose that this line belonged to a new element. He named the element helium after "helios," the Greek word for the Sun.

It took several more decades to find helium on our own planet. In 1881, Italian physicist Luigi Palmieri detected helium in material from an eruption of Mount Vesuvius. The formal isolation of the element occurred in 1895. Scottish chemist Sir William Ramsay isolated helium by treating a mineral called cleveite with mineral acids.

William Ramsay working
William Ramsay working

Cleveite is a variety of uraninite containing rare-earth elements. At the same time, chemists Per Teodor Cleve and Nils Abraham Langlet independently isolated the gas in Sweden. They collected enough to determine its atomic weight. This discovery proved that the element Lockyer saw in the Sun actually existed on Earth.

Scientists have also studied the extreme physical properties of helium. In 1908, Dutch physicist Heike Kamerlingh Onnes succeeded in liquefying helium. He did this by cooling the gas to temperatures below 4 Kelvin.

2 Helium
2 Helium

Interestingly, he found that helium would not solidify at standard atmospheric pressure. It was not until 1926 that Willem Hendrik Keesom successfully solidified a small amount of helium. He achieved this by applying additional external pressure. Today, researchers study the different fluid phases of helium-4, known as helium I and helium II. These phases are important for understanding quantum mechanics and the property of superfluidity. Superfluidity allows the liquid to behave in strange ways, such as creeping along surfaces.

helium-II-creep
helium-II-creep

Helium has many vital industrial and scientific applications. One of its largest uses is in cryogenics, which is the study of very low temperatures. About one-quarter of all helium production is used for this purpose. It is specifically used to cool superconducting magnets in MRI scanners.

Modern 3T MRI
Modern 3T MRI

Other industrial uses include providing a protective atmosphere for arc welding. It is also used in processes to grow crystals for silicon wafers. Because helium is so light and does not burn, it is a common lifting gas for balloons and airships.

Goodyear-blimp
Goodyear-blimp

Despite its many uses, helium is a non-renewable resource on Earth. Because it is so light, once it is released into the atmosphere, it quickly escapes into space. Most of our supply comes from natural gas fields, such as those found in the United States. In these fields, helium can reach concentrations as high as 7% by volume. We extract it using a low-temperature process called fractional distillation. Because our supply is rapidly diminishing, managing this precious element is a major concern for science and industry.

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🖼️ Images & Media (14)
File:Helium spectrum.jpg
Helium spectrum.jpg
File:William Ramsay working.jpg
William Ramsay working.jpg
File:Kansas Helium Marker.jpg
Kansas Helium Marker.jpg
File:Helium atom QM.svg
Helium atom QM.svg
File:Binding energy curve - common isotopes.svg
Binding energy curve - common isotopes.svg
File:HeTube.jpg
HeTube.jpg
File:Phase diagram of Helium-4-en.svg
Phase diagram of Helium-4-en.svg
File:2 Helium.png
2 Helium.png
File:helium-II-creep.svg
helium-II-creep.svg
File:Helium-hydride-cation-3D-SF.png
Helium-hydride-cation-3D-SF.png
File:Fluoroheliate-ion-3D-vdW.png
Fluoroheliate-ion-3D-vdW.png
File:Modern 3T MRI.JPG
Modern 3T MRI.JPG

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