Helium

Helium was first observed in 1868 during a solar eclipse by French astronomer Pierre Janssen, who detected a bright yellow spectral line indicative of an unknown element in sunlight. This discovery was confirmed by English chemist Sir William Ramsay in 1895 when he isolated the gas from uranium minerals on Earth. The name 'helium' comes from the Greek 'helios,' which means sun. Helium's role in the cosmos was cemented when scientists realized it constituted about 25% of the universe's baryonic mass.

Helium is primarily found in natural gas deposits, where it is concentrated due to the decay of radioactive elements like uranium and thorium. It is also released during the extraction of oil and natural gas, and can be produced in trace amounts through the radioactive decay of heavy elements in the Earth's crust. Helium constitutes about 0.0005% of the Earth's atmosphere, making it relatively rare in our immediate environment but abundant in the universe, especially in stars.

Helium does not play a direct biological role in human or animal physiology, as it is non-toxic and chemically inert. However, it is useful in various medical applications, including magnetic resonance imaging (MRI), as it helps cool the superconducting magnets used in the machines. Helium's low density makes it a safe alternative to hydrogen in ballooning and aerostatics, minimizing the risk of combustion and explosion.

Helium is a colorless and tasteless gas that remains in its gaseous state at extremely low temperatures, solidifying only under high pressure. Its boiling point is approximately -268.9 degrees Celsius, making it the element with the lowest boiling point. Helium exhibits low density, which contributes to its tendency to rise in the atmosphere. Chemically, helium is characterized by its complete lack of reactivity because it has a full outer electron shell, aligning it with the properties typical of noble gases.

The most prominent application of helium is in the field of cryogenics, particularly in cooling superconducting magnets for MRI machines and particle accelerators. Additionally, helium is used in balloons, airships, and blimps due to its lighter-than-air properties and non-flammability. It is also a crucial component in certain types of lasers and in the production of fiber optics. Moreover, helium can be used in gas chromatography and as a protective shield in welding processes.

• Helium is the second most abundant element in the universe after hydrogen.
• It was first discovered in the spectrum of sunlight before being found on Earth.
• Helium is so light that if a balloon filled with helium is released, it can rise to altitudes higher than 30,000 meters.
• Liquid helium is the coldest substance known, achieving temperatures close to absolute zero.
• Helium is used in deep-sea breathing mixtures to reduce the risk of nitrogen narcosis.