What is Helium

Helium (pronunciation: HEE-lee-em) is a colorless, odorless element classified as a non-metal, belonging to the group of inert gases in the periodic table and is represented by the chemical symbol He ^{[1, 2, 3]}. It is a monoatomic gas that forms weak diatomic molecules only at temperatures close to -273.15 °C or “the absolute zero” ^[4].

Isotopes

Helium has nine known isotopes out of which ³He and ⁴He are stable with natural abundances of about 0.0002% and 99.9998% respectively ^[5]. Its radioactive isotopes are short-lived, with ⁶He being the longest-lived characterized by a half-life period of 806.7 milliseconds while ⁵He is the least stable with a half-life period of 7.6 X 10^-22 seconds ^[5].

Where is Helium Found

Helium is the second-most abundant element found in the universe only after hydrogen ^[1]. It is found in all stars and is formed on the Earth from radioactive elements when they undergo alpha-decay ^[1]. For natural dynamic balance, the low-density helium escapes into the Earth’s atmosphere and then to outer space ^[1]. The price of extracting the element from the air is very high, and so, it is commercially obtained from natural gas that can contain about 7% helium by volume ^[1].

The top 3 helium producers are USA, Algeria, and Russia while top helium reserve holding countries include USA, Qatar, and Algeria ^[1].

History

Origin of its Name: It is derived from ‘Helios’, Greek for the Sun, as it was first identified as the gas that constitutes the Sun’s corona ^[1]

Who discovered it: The element was discovered by the Scottish chemist Sir William Ramsay and independently by the Swedish chemists Nils Abraham Langlet and Per Teodor Cleve ^{[1, 2]}.

When and How was it Discovered

Before the discovery of helium on Earth, it was found on the Sun ^[2]. In 1868, the French astronomer Pierre Janssen studied a total solar eclipse in India and found a yellow line while measuring the Sun’s spectrum ^{[1, 2]}. An English astronomer, Sir Joseph Norman Lockyer, also observed the same spectral line and presumed that it was caused by an unknown metallic element, which he named helium ^{[1, 2]}.

In 1895, William Ramsay experimented with cleveite, a radioactive mineral containing uranium and collected the gas that formed after its dissolution in sulfuric acid ^{[1, 2]}. He sent the sample to Sir William Crookes and Norman Lockyer, who identified the helium within it ^[2]. In 1895, at Uppsala, Sweden, Abraham Langlet and Teodor Cleve independently collected the gas produced after dissolving uraninite (UO₂) in acid ^{[1, 2]}. They found its atomic weight and declared that it was helium ^[1].

Helium Identification
Atomic number	2 [1]
CAS number	7440-59-7 [1]
Position in the periodic table	Group	Period	Block
	18 [1]	1 [1]	s [1]

Properties and Characteristics of Helium

Atomic Data of Helium (Element 2)

What is Helium Used for

• As a coolant, helium is used in MRI scanners’ superconducting magnets, NMR spectrometers, and the Large Hadron Collider ^[1]. It is used to cool instruments in satellites and space vehicles ^[1].
• The gas is used to fill weather balloons, airships, and decorative blimps due to its low density ^{[1, 4]}. Despite hydrogen being more buoyant and cheaper, helium is preferred because it is non-flammable ^[15].
• It can be used for pressurizing and cooling the liquid fuel (liquid hydrogen) in rockets and space vehicles ^{[1, 4]}.
• Since helium is extremely unreactive by nature, it can provide a protective atmosphere for arc welding, as well as manufacturing semiconductors and fiber optics ^{[1, 4]}.
• For people working under pressurized conditions, like deep-sea divers, 80% helium is mixed with 20% oxygen to create an artificial atmosphere ^{[1, 4]}. Divers use helium because it leaves their body faster as compared to nitrogen, helping in faster decompression ^[4].
• It is used for detecting leaks in air-conditioning systems of automobiles and for inflating car airbags after the accident ^[1].
• Helium-neon laser barcode scanners are used in supermarket checkouts ^[1].
• Electron microscopes are now replaced by helium-ion microscopes for their better image resolution ^[1].

Helium Toxicity and Health Effects

Helium is not known to be toxic and does not play any biological role ^[1]. Although it is commonly believed that inhaling it causes the voice to temporarily become high-pitched ^{[4, 12]}, heavily inhaling helium can cause an obstruction, cutting off oxygen supply ^[13].

Interesting Facts

• The graphical representation of helium shows the Sun, indicating the origin of its name from the Greek word ‘Helios’ and its presence in the Sun ^[1].
• The Federal Helium Reserve near Amarillo, Texas has about 40% of the helium gas used by the Americans in a year ^[3].
• Since helium turns into a superfluid state at about -271 °C, it is used by the scientists for studying the behavior of superfluids ^[3].

Cost of Helium

While the price of pure helium is about $0.052 per gram, liquid helium costs roughly $5 per liter ^{[4, 14]}.

References
1. http://www.rsc.org/periodic-table/element/2/helium
2. https://education.jlab.org/itselemental/ele002.html
3. https://www.livescience.com/28552-facts-about-helium.html
4. https://www.chemicool.com/elements/helium.html
5. https://education.jlab.org/itselemental/iso002.html
6. https://www.webqc.org/molecular-weight-of-helium.html
7. https://pubchem.ncbi.nlm.nih.gov/compound/helium
8. https://hobart.k12.in.us/ksms/PeriodicTable/helium.htm
9. http://periodictable.com/Elements/002/data.html
10. https://www.easycalculation.com/chemistry/oxidation-number-helium.html
11. http://chemistry-reference.com/q_elements.asp?Symbol=He&language=en
12. https://www.medscape.com/viewarticle/760299
13. https://www.medscape.com/viewarticle/760299
14. https://physicstoday.scitation.org/doi/pdf/10.1063/PT.3.3424
15. https://www.independent.co.uk/news/science/why-the-world-is-running-out-of-helium-2059357.html