Let's Know the Elements: What is Helium, Where is it Used? What are the Properties of Helium?

Helium Element
Helium Element

Helium (Greek: λλιος, romanized: helios, lit. 'the sun') is a chemical element with symbol and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and ranks first in the noble gas group in the periodic table, and has the lowest boiling and melting point of all elements.

Atomic Structure of Helium

In terms of quantum mechanics, helium is the second simplest atom to model, following the hydrogen atom. Helium consists of two electrons in atomic orbitals surrounding a nucleus containing two protons and (usually) two neutrons. As in Newtonian mechanics, no system consisting of more than two particles can be solved by a precise analytical mathematical approach, and helium is no exception. Therefore, numerical mathematical methods are necessary even to solve the one nucleus and two electron system. Such computational chemistry methods have been used to construct a quantum mechanical picture of helium electron bonding correct within <2% of the correct value in several computational steps.

These models show that each electron in helium partially eliminates the nucleus from the other, so that the effective nuclear charge Z seen by each electron is about 2 units, not the 1.69 charges of a classical "bare" helium nucleus.

The Place of Helium in the Universe

It is the second lightest and second most abundant element in the observable universe (hydrogen is the lightest and most abundant). It is present in about 24% of the total elemental mass; this is more than 12 times the mass of all the heavy elements combined. Its abundance is similar to that in both the Sun and Jupiter, due to the very high nuclear binding energy (per nucleon) of helium-4 relative to the three next elements helium. This helium-4 binding energy also explains why it 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 formed by the nuclear fusion of hydrogen in stars.

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

Janssen is often credited with detecting the element with Norman Lockyer. Janssen recorded the helium spectral line during the 1868 solar eclipse, while Lockyer observed it from England. Lockyer was the first to suggest that the line originated from a new element he named. The element's official discovery was made in 1895 by chemists Sir William Ramsay, Per Teodor Cleve, and Nils Abraham Langlet, who found helium extracted from uranium ore, cleveite, which is not currently considered a separate mineral species, but a variety of uraninite. In 1903, large reserves of helium were found in natural gas fields in parts of the United States, the largest supplier of gas to date.

Applications of Helium

Liquid helium is used in cryogenics (its largest single use, absorbing about a quarter of production) and cooling superconducting magnets, with its main commercial application in MRI scanners. Other industrial uses of helium — as a pressurization 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. As with any gas whose density is different from air, breathing in a small volume of helium temporarily alters the timbre and quality of the human voice. In scientific research, the behavior of the two fluid phases of helium-4 (helium I and helium II) is important for researchers studying quantum mechanics (especially the property of superfluidity) and for those looking at phenomena such as superconductivity produced in near absolute zero matter.

What are the Properties of Helium?

It is relatively rare on Earth — 5.2 ppm by volume in the atmosphere. Most terrestrial helium available today is created by the natural radioactive decay of heavy radioactive elements (thorium and uranium, although there are other examples), because the alpha particles emitted by such decays are composed of helium-4 nuclei. This radiogenic helium is trapped with natural gas at concentrations of up to 7% by volume and is commercially extracted from there by a low temperature separation process called fractional distillation. Terrestrial helium is a non-renewable resource because after it is released into the atmosphere, it immediately escapes into space. However, some studies show that helium produced deep within the Earth by radioactive decay may be collected in larger-than-expected amounts in natural gas reserves, in some cases released by volcanic activity.

Obtaining Helium

Helium, a colorless, odorless and tasteless inert gas, is the second most abundant gas in the universe after hydrogen gas. However, the type of helium gas used in applications such as gas chromatography is extracted from natural gas – a problem of depletion of resources leading to helium gas shortages.

Helium gas is abundant in space – a byproduct of fusion reactions that occur inside stars. However, the helium gas we can find on earth and stored in helium gas tanks for later use in many critical applications is limited. This type of helium gas, called helum-4, is produced naturally underground through the radioactive decay and decay of certain elements such as uranium and thorium. The result of this reaction are alpha particles containing two neutrons and a proton. These tiny bits then pick up electrons from their surroundings and then pass through the earth's crust to form helium, which extends into space.

Luckily, some of the helium-4 gets trapped and mixes with natural gas beneath the layers below the earth's surface. Helium-4 is then extracted from the ground by wells drilled for its release. The amount of helium gas that can be found in natural gas varies from almost negligible to 4% by volume. Natural gas containing helium-4 is then subjected to a cryogenic distillation process to obtain helium particles. After separating from natural gas, helium-4 goes through another refining process and is then brought to 99,99+% purity for market sale.

Source: Wikipedia, peakscientific

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