Helium is an essential element with unique properties that have made it indispensable in a variety of fields, from medicine and aerospace to cryogenics and welding. While helium is the second most abundant element in the universe, its scarcity on Earth poses challenges to its continued use in many industries. The ongoing helium shortage emphasizes the need for sustainable methods of extraction and utilization.
Helium (He) is a chemical element in the periodic table with the atomic number 2. It is the second lightest element in the universe and is classified as a noble gas. Helium is colorless, odorless, tasteless, non-toxic, inert, and the second most abundant element in the observable universe. Despite its abundance in space, Helium is relatively rare on Earth, and its unique properties have led to its widespread use in various industries and scientific fields.
Discovery of Helium
Helium was first discovered in 1868 by the French astronomer Pierre Janssen, who detected it in the solar spectrum during a solar eclipse. He observed a yellow spectral line that did not correspond to any known element, suggesting the presence of a new element. In the same year, Sir William Ramsay, a British chemist, discovered helium on Earth when he isolated it from a mineral called cleveite. Ramsay’s discovery of helium on Earth confirmed Janssen’s solar observation, and the element was named “helium” after the Greek god Helios, the personification of the Sun.
Properties of Helium
- Physical Properties:
- Atomic Number: 2
- Atomic Mass: 4.0026 u
- Density: 0.1786 g/L (at 0°C and 1 atm pressure)
- State: Gas (at standard temperature and pressure)
- Color: Colorless
- Odor: Odorless
- Taste: Tasteless
- Boiling Point: −268.93°C (4.22 K)
- Melting Point: −272.2°C (0.95 K)
- Solubility: Very low solubility in water
- Isotopes: Helium has two stable isotopes, Helium-3 and Helium-4.
- Chemical Properties:
- Inertness: Helium is an inert gas and does not readily form compounds with other elements. Its stability comes from its full electron shell (two electrons in the 1s orbital), making it chemically unreactive.
- Non-Flammable: Unlike hydrogen, helium is non-flammable and does not support combustion.
- Low Reactivity: Helium rarely participates in chemical reactions, making it highly stable.
- Quantum Properties:
- Helium is the only element that does not solidify at atmospheric pressure, even at extremely low temperatures. It remains in a liquid state down to absolute zero under normal pressures.
- Superfluidity: Below 2.17 K, Helium-4 exhibits superfluidity, a state of matter where it flows without viscosity. This phenomenon is a subject of intense study in physics.
Occurrence of Helium
Helium is the second most abundant element in the universe, forming about 24% of its mass. It is primarily produced through the nuclear fusion of hydrogen in stars, especially in our Sun. In the Sun’s core, hydrogen atoms fuse to form helium, releasing energy. This process of fusion provides the Sun with its energy.
On Earth, helium is relatively rare. It is typically found in trace amounts in natural gas deposits, where it is produced by the radioactive decay of elements such as uranium and thorium. These decays produce alpha particles, which eventually form helium atoms. Helium is extracted from these natural gas deposits through a process of cryogenic distillation.
Uses of Helium
Helium has a wide range of applications due to its unique properties:
- Cryogenics:
- Helium’s low boiling point makes it essential for use in cryogenics, particularly in cooling superconducting magnets used in MRI (Magnetic Resonance Imaging) machines and particle accelerators.
- Balloon Filling:
- Helium is widely used to fill balloons and airships because it is lighter than air and non-flammable. This is particularly important for safety, as hydrogen, which was previously used, is highly flammable.
- Aerospace:
- Helium is used in the aerospace industry for inflating satellites and rockets. It is also used as a pressurizing agent for fuel tanks and to purge fuel lines during rocket launches.
- Welding and Metal Industry:
- Helium is used as an inert gas in welding because it does not react with the metals being welded, providing a clean and stable environment for the process.
- Medical Applications:
- Helium is used in medical respiratory therapy. A mixture of helium and oxygen (Heliox) is used for patients with breathing difficulties or conditions like asthma and COPD.
- Scientific Research:
- Due to its low atomic mass and superfluidity, helium is used in experiments that explore quantum mechanics and low-temperature physics.
- Leak Detection:
- Helium is used for leak detection in vacuum systems and other sealed environments due to its small atomic size and ability to seep through tiny cracks.
- Refrigeration:
- Helium is used in ultra-low temperature refrigeration systems, especially for cooling the superconducting magnets of MRI machines and in other scientific research.
Helium Shortage
Despite its abundance in the universe, helium is a finite resource on Earth. The process of extracting and storing helium is expensive, and it is also a non-renewable resource. As a result, there have been growing concerns over a helium shortage. This shortage is due to the limited number of natural gas fields containing helium and the fact that once released into the atmosphere, helium escapes into space and cannot be recovered.
