Helium

Helium, a noble gas, is distinguished by its low density. It is the second lightest element in the periodic table, surpassed only by hydrogen. This low density is a result of its atomic structure, which consists of two protons and, in its most common isotope, two neutrons.

One of the defining characteristics of helium is its low reactivity. This is due to its full valence electron shell, which makes it chemically stable and resistant to forming compounds with other elements. As a result, helium is often used in environments where chemical reactions are undesirable, such as in the cooling of superconducting magnets or as a protective atmosphere in the manufacturing of semiconductors.

In terms of abundance, helium is second only to hydrogen in the universe. This is largely due to the process of stellar nucleosynthesis, in which helium is produced through the fusion of hydrogen atoms in stars.

Despite its abundance in the universe, helium is relatively rare on Earth, as it tends to escape from the atmosphere into space due to its low density.

The first evidence of helium was found by Pierre Janssen (also known as Jules Janssen) and Norman Lockyer, who independently observed a yellow line in the Sun's spectrum. This discovery was made possible by the use of spectroscopy, a technique that allows the identification of elements based on the unique patterns of light they emit or absorb.

The first observation of helium was made during a solar eclipse in 1868. This event provided the ideal conditions for Janssen to observe the Sun's spectrum without the interference of the Earth's atmosphere.

It was during this observation that he noticed a yellow spectral line that could not be attributed to any known element, leading to the discovery of helium. Lockyer subsequently confirmed Janssen’s findings when he viewed the sun’s spectrum through the smog of London.

The name helium is derived from the Greek word 'Helios', which means Sun. This name was chosen to reflect the element's place of discovery and its association with solar phenomena. Despite its initial discovery in the Sun, helium is now known to be present in various locations throughout the universe, including other stars, natural gas deposits, and the Earth's atmosphere.

The atomic structure of helium is characterized by the presence of two protons, which gives it an atomic number of two.

The most common isotope of helium, helium-4, has two neutrons in addition to its two protons. This isotope accounts for nearly all of the naturally occurring helium on Earth.

The presence of two neutrons in the nucleus of a helium-4 atom contributes to its stability, as the neutrons help to offset the repulsive forces between the protons.

One of the most unique properties of helium is that it cannot be solidified by lowering the temperature at normal pressure. This is due to the fact that helium remains a liquid down to absolute zero at normal pressure, a property shared by no other element. This behavior is a result of quantum mechanical effects, specifically the principle of zero point energy.

Despite its placement in the p-block of the periodic table, helium is unique in that its highest energy electrons are in the 1s orbital, not a p orbital. This is due to helium's low atomic number, which means it only has two electrons to fill its orbitals. These electrons both occupy the 1s orbital, which is the lowest energy orbital available.

Helium is found in group 18 of the periodic table, a group collectively termed the noble gases. These elements, which also include neon, argon, krypton, xenon, and radon, are characterized by their full valence electron shells, which make them chemically stable and unreactive.

The noble gases are colorless, odorless, tasteless, and nonflammable. They also have low chemical reactivity, which makes them ideal for use in situations where chemical reactions are undesirable.

Despite their lack of color, noble gases can emit colorful light when electrically charged, a property that is utilized in neon lights and other types of lighting.

Helium is formed in stars through the process of nuclear fusion of hydrogen. This process involves the combination of hydrogen nuclei to form helium, releasing a large amount of energy in the process. This energy is what powers stars and makes them shine.

The process of stellar nucleosynthesis, which involves the fusion of hydrogen atoms to form helium, is a primary source of helium in the universe. However, the majority of helium-4 in the universe was actually formed during the big bang, a testament to the element's longevity and stability.

The Sun, like other stars, is composed of approximately 25% helium by mass. This helium is continually being produced through the fusion of hydrogen in the Sun's core. The remaining 75% of the Sun's mass is primarily hydrogen, which serves as the fuel for the ongoing nuclear fusion reactions.

Alpha decay, which results in the emission of helium-4 nuclei, is a key process in the production of helium on Earth. Over billions of years, the helium produced by alpha decay has accumulated in the Earth's crust, where it can be extracted from natural gas deposits.

The Earth's crust contains significant amounts of helium that has been built up over billions of years of radioactive decay. Around 99% of the helium produced on Earth comes from the radioactive decay of uranium and thorium in minerals underground.

This helium is often trapped in natural gas deposits. During natural gas production, these helium deposits are brought to the surface as a by-product. The helium can then be extracted and used.

However, once released into the atmosphere, helium can escape into space due to its low density.

One of the primary uses of helium is in cryogenics, a branch of science dealing with very low temperatures, where it serves as a coolant for superconducting magnets. These magnets are used in a variety of applications, including magnetic resonance imaging (MRI) machines and particle accelerators. Helium's low boiling point makes it ideal for achieving the extremely low temperatures required for superconductivity.

Due to its low density, helium is often used in lighter-than-air balloons. When a balloon is filled with helium, it becomes lighter than the surrounding air and can float. This property is also utilized in airships and weather balloons.

Helium has a number of other uses. In deep-sea diving, helium is used in breathing gas mixtures to reduce the risk of nitrogen narcosis, also known as 'the bends', a dangerous condition that can occur when divers breathe compressed air at depth.

In the semiconductor industry, helium's low reactivity makes it ideal for creating a protective atmosphere during the manufacturing process.

The Large Hadron Collider is the biggest particle accelerator in the world. It is used to conduct experiments in particle physics, colliding subatomic particles at extreme energy levels, to answer questions about the building blocks of matter and our universe.

The use of helium in the Large Hadron Collider helps to maintain the extremely low temperatures necessary for its operation. Without helium, it would be impossible to achieve the conditions necessary for the superconducting magnets to function, and the collider would not be able to operate.

In 2008, a leak of helium caused a significant delay in the start-up of the Large Hadron Collider. This incident highlighted the importance of helium for the operation of the collider.

There are growing concerns about a potential shortage of helium due to its increasing use in various industries. Helium has applications in a wide range of industries, including healthcare, in the production of electronic devices and the manufacture of fiber optics, and even in space exploration.

The rate of helium's replenishment in the atmosphere is slow, as it is primarily produced through natural radioactive decay. This slow rate of replenishment, combined with increasing demand, has led to concerns about the long-term availability of helium.

Unlike other gases, helium does not contribute to the greenhouse effect or ozone layer depletion. However, the release of helium into the atmosphere can contribute to its depletion as a resource. The supply of helium on Earth is finite, and once released into the atmosphere, it can escape into space and be lost forever. There is growing concern that we are running out of useable helium on earth. Helium is an increasingly scarce resource, which will pose problems in areas such as healthcare, where it is highly valuable.