Helium
Overview
Helium (symbol He) is the second element on the periodic table, a colorless, odorless, tasteless noble gas. With a boiling point of -268.93°C, the lowest of all elements, liquid helium is essential for advanced technology and medical fields, including cooling superconductors, MRI (magnetic resonance imaging), semiconductor manufacturing, and pressurizing space rocket fuel tanks. It is extremely rare in Earth's atmosphere at about 5.2 ppm (by volume), but is the second most abundant element in the universe after hydrogen.
Main Content
Discovery and History
Helium was first identified in 1868 when French astronomer Pierre Janssen observed a yellow line in the solar spectrum during a total solar eclipse in India. That same year, British astronomers Norman Lockyer and Edward Frankland attributed this line to a new element, naming it 'helium' after the Greek sun god Helios. On Earth, helium was isolated in 1895 by Scottish chemist William Ramsay from cleveite (a uranium mineral).
Physical and Chemical Properties
- Atomic number: 2
- Atomic mass: 4.002602 u
- Density: 0.1785 g/L (0°C, 1 atm) – about 7 times lighter than air
- Boiling point: -268.93°C (4.22 K)
- Melting point: -272.2°C (0.95 K, at 26 atm) – remains liquid at atmospheric pressure down to absolute zero
- Inertness: The least reactive element, forming almost no compounds. However, helium-neon compounds (HeNe) have been reported at extremely low temperatures and high pressures.
- Superfluidity: Liquid helium-4 becomes a superfluid (zero viscosity) below 2.17 K, exhibiting the 'fountain effect' where it flows up and over container walls.
Production and Supply
Helium is primarily extracted from natural gas fields, where it accumulates from the radioactive decay of uranium and thorium. The world's largest helium producers are the United States (especially Texas, Kansas, and Oklahoma), Qatar, Algeria, and Russia. The U.S. Federal Helium Reserve (BLM) once managed about 30% of global supply, but market volatility increased after its privatization in 2021. Helium is liquefied at extremely low temperatures (about -269°C) for transport in tanks and refined to high purity (99.999% or higher).
Major Uses
1. Medical: Liquid helium cools the superconducting magnets in MRI scanners, accounting for about 30% of global helium consumption.
2. Semiconductor/Electronics: Used as a protective gas, coolant, and for leak detection in silicon wafer manufacturing.
3. Space/Aerospace: Pressurizes rocket fuel tanks (especially liquid hydrogen and oxygen), operates gas valves, and cools satellites.
4. Welding/Metallurgy: Serves as a shielding gas in arc welding (mixed with argon) and in the production of titanium and aluminum alloys.
5. Scientific Research: Used in cryogenic physics experiments, cooling particle accelerators (e.g., CERN LHC), and nuclear magnetic resonance (NMR) spectrometers.
6. Other: Weather balloons (radiosondes), diving gas mixtures (trimix), and lifting gas for balloons and airships.
Environmental and Economic Importance
Helium is a non-renewable resource on Earth; once released into the atmosphere, its low gravity allows it to escape permanently into space. Thus, helium is classified as a 'strategic scarce resource' with highly volatile prices. Since the 2010s, several helium shortages have disrupted research and medical fields. Recycling technologies (liquid helium re-liquefaction systems) have been developed, but over 70% of consumed helium is still lost to the atmosphere without recovery.
Latest Trends
As of 2024-2025, the helium market is undergoing the following changes:
- Supply chain diversification: To reduce dependence on the U.S., new production sites are expanding in Qatar (Ras Laffan plant expansion), Russia (Amur Gas Processing Plant, full operation in 2025), and Tanzania (new exploration).
- Price stabilization efforts: Helium prices, which surged in 2022-2023, have slightly declined in 2024 but remain near historical highs. Market predictability has decreased since BLM's privatization.
- Advances in recycling: Medical institutions and research labs are increasingly adopting helium re-liquefaction equipment; some large MRI centers report recycling over 90% of their consumption.
- Alternative technology research: Development of high-temperature superconductors (MgB2, REBCO) is leading to MRI systems that do not require helium cooling, entering commercialization (some products expected in 2025). This innovation could reduce long-term helium demand.
- Tighter regulations: The EU and U.S. are discussing helium export controls and mandatory stockpiling laws; the U.S. Congress is expected to reintroduce the 'Helium Conservation and Innovation Act' amendment in 2025.
Related Topics
- [[Noble gas]]
- [[Superconductor]]
- [[MRI]]
- [[Space industry]]
- [[Resource depletion]]
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