Helium:Introduction ,Discovery ,Chemical and Physical Properties ,Occurrence ,Production ,Uses and Significance
Helium is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert monatomic gas that heads the noble gas group in the periodic table. Helium is the second lightest and second most abundant element in the observable universe, after hydrogen. It is a key component in various scientific, industrial, and medical applications due to its unique properties. Despite its abundance in the universe, helium is relatively rare on Earth, making it a valuable resource.
Discovery of Helium
Early Observations
The discovery of helium is a fascinating story that began in the 19th century. Unlike many other elements, helium was first detected in space before it was found on Earth. In 1868, French astronomer Pierre Janssen observed a yellow spectral line in the light emitted by the Sun during a solar eclipse in Guntur, India. This line did not correspond to any known element at the time. Janssen initially thought it might be sodium, but further analysis revealed it was something entirely new.
Identification and Naming
Around the same time, English astronomer Norman Lockyer independently observed the same spectral line and concluded that it represented a new element. Lockyer named the element "helium" after the Greek god of the Sun, Helios. The discovery marked the first time an element was identified in space before being found on Earth.
Isolation on Earth
Helium was first isolated on Earth in 1895 by Scottish chemist Sir William Ramsay and Swedish chemists Per Teodor Cleve and Abraham Langlet. They independently isolated helium by treating the mineral cleveite (a uranium-containing mineral) with acids and observing the resulting gases. Ramsay's work confirmed that helium was a new element and not a compound.
Properties of Helium
Physical Properties
Helium is unique among the elements due to its remarkable physical properties:
State at Room Temperature: Helium is a gas at room temperature and pressure. It remains in a gaseous state under standard conditions, unlike most other elements.
Boiling and Melting Points: Helium has the lowest boiling point (-268.93°C or 4.22 K) and melting point (-272.20°C or 0.95 K) of all the elements. It is the only element that cannot be solidified by cooling at standard pressure.
Density: Helium is less dense than air, with a density of 0.1785 g/L at standard temperature and pressure (STP). This makes it lighter than most other gases.
Thermal Conductivity: Helium has high thermal conductivity, making it an excellent coolant.
Superfluidity: At temperatures close to absolute zero, helium-4 exhibits superfluidity, a state in which it flows without viscosity. This property is unique to helium and has significant implications in quantum mechanics.
Chemical Properties
Helium is a noble gas, which means it is chemically inert under most conditions. Its chemical properties include:
Inertness: Helium does not readily form compounds with other elements due to its complete valence electron shell. It has a full outer shell with two electrons, making it highly stable.
Lack of Reactivity: Helium does not participate in chemical reactions under normal conditions. It does not burn, corrode, or react with other substances.
Isotopes: Helium has two stable isotopes: helium-4 (the most abundant) and helium-3. Helium-3 is rare on Earth but has unique properties, such as the ability to become a superfluid at even lower temperatures than helium-4.
Occurrence of Helium
In the Universe
Helium is the second most abundant element in the universe, accounting for about 24% of the elemental mass. It is primarily formed through nuclear fusion in stars, where hydrogen atoms fuse to form helium under extreme temperatures and pressures. This process, known as the proton-proton chain reaction, is the primary source of helium in the universe.
On Earth
Despite its abundance in the universe, helium is relatively rare on Earth. It is found in trace amounts in the atmosphere (about 5.2 parts per million by volume). Most of the helium on Earth is produced through the radioactive decay of heavy elements such as uranium and thorium. This process releases alpha particles, which are essentially helium nuclei. Over time, these particles capture electrons to form helium gas.
Natural Gas Reservoirs
The primary source of helium on Earth is natural gas reservoirs. Helium accumulates in these reservoirs as a byproduct of radioactive decay. The largest helium reserves are found in the United States, Qatar, Algeria, and Russia. The Hugoton Gas Field in the United States is one of the most significant sources of helium.
Production of Helium
Extraction from Natural Gas
Helium is extracted from natural gas through a process called fractional distillation. This process involves the following steps:
Gas Separation: Natural gas is first processed to remove impurities such as water, carbon dioxide, and hydrocarbons.
Cooling and Compression: The gas is cooled and compressed to liquefy most of its components.
Fractional Distillation: The liquefied gas is subjected to fractional distillation, where it is separated into its constituent components based on their boiling points. Helium, having a very low boiling point, remains gaseous and is collected.
Purification
The collected helium gas is further purified to remove any remaining impurities. This is typically done through processes such as pressure swing adsorption (PSA) or membrane separation.
Storage and Transportation
Helium is stored and transported in high-pressure cylinders or cryogenic containers to maintain its gaseous or liquid state. Due to its low density, helium can escape from containers if not properly sealed.
Uses of Helium
Scientific Research
Cryogenics: Helium is widely used as a coolant in cryogenics due to its extremely low boiling point. It is essential for cooling superconducting magnets in devices such as MRI machines and particle accelerators.
Quantum Mechanics: Helium's superfluidity makes it a valuable tool for studying quantum mechanics and low-temperature physics.
Medical Applications
MRI Machines: Helium is used to cool the superconducting magnets in MRI machines, enabling high-resolution imaging of the human body.
Respiratory Treatments: A mixture of helium and oxygen, known as heliox, is used to treat respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD).
Industrial Applications
Leak Detection: Helium is used as a tracer gas to detect leaks in pipelines, vacuum systems, and other sealed containers.
Welding: Helium is used as a shielding gas in arc welding to protect the weld area from atmospheric contamination.
Balloons and Airships: Helium is used to fill balloons and airships due to its low density and non-flammability.
Aerospace and Defense
Rocket Propulsion: Helium is used to pressurize fuel tanks in rockets and spacecraft.
Aircraft: Helium is used in air-to-air missile systems and other defense applications.
Other Uses
Diving: Helium is used in breathing mixtures for deep-sea diving to prevent nitrogen narcosis.
Electronics: Helium is used in the production of semiconductors and fiber optics.
Significance of Helium
Economic Importance
Helium is a valuable resource with significant economic importance. Its unique properties make it indispensable in various high-tech industries, including healthcare, aerospace, and electronics. The global helium market is worth billions of dollars, and demand continues to grow.
Scientific Importance
Helium plays a crucial role in advancing scientific research. Its use in cryogenics and quantum mechanics has led to groundbreaking discoveries and technological innovations. For example, the development of MRI technology would not have been possible without helium.
Environmental Concerns
Helium is a non-renewable resource, and its extraction and use have raised environmental concerns. The depletion of helium reserves could have far-reaching consequences for industries that rely on it. Efforts are underway to develop sustainable methods for helium production and recycling.
Conclusion
Helium is a remarkable element with unique properties that make it invaluable in a wide range of applications. From its discovery in the Sun to its use in cutting-edge technologies, helium has played a pivotal role in shaping our understanding of the universe and advancing human progress. As we continue to explore its potential, it is essential to balance its use with sustainable practices to ensure its availability for future generations.
Photo from iStock
0 Comment to "Helium : Introduction ,Discovery ,Chemical and Physical Properties ,Occurrence ,Production ,Uses and Significance "
Post a Comment