Prelims cum Mains Science & Tech

Helium turns 150 on August 18, 2018

The News

  • Helium was discovered 150 years ago in 1868 by French astronomer Pierre Janssen during a solar eclipse using spectroscope.

 

About Helium

  • Helium is the second-lightest and second most common element in the universe after hydrogen gas.
  • Helium belongs to the group of noble gases that occupy the far right hand side of the periodic table.
  • It is the most unreactive (inert) element in the periodic table.
  • Low chemical reactivity is due to a stable electron arrangement (filled outer shell of electrons).

 

Helium in our solar system

  • Helium is a major component of Sun’s atmosphere.
  • It is not abundant on earth because Earth’s gravity is not strong enough to hold a light element like helium.
  • Helium is a major component of the gas giants like Jupiter and Saturn as they are bigger planets with stronger gravity.

 

Helium on Earth

  • Helium was discovered on Earth inside cleveite which is a uranium-based mineral.
  • Helium is mostly trapped beneath the surface of the earth in radioactive rocks of uranium and thorium.
  • As uranium and thorium decay, they release alpha particles which are nothing but helium nucleus.
  • These alpha particles mop up electrons and make helium.

 

Important properties of Helium

  • Helium is a very stable element being chemically inert and nonreactive.
  • It is nonflammable and nonpoisonous.
  • Most importantly, it boils at 4.2 Kelvin, or minus 268 degrees Celsius which is the lowest temperature possible in the universe.
  • No other element can remain a liquid at these temperatures.

 

 

Applications

Super conductors and Helium:

  • Materials that conduct electricity well such as metals are called conductors.
  • The electrons flow inside a metal with some friction. This friction is called resistance.
  • Superconductors are conductors that have zero resistance .i.e. they don’t impede electricity at all.
  • However, all known superconductors have the zero resistance property only at low temperatures.
  • The original superconductors are kept cold by immersing them in liquid helium.

Significance in MRI and NMR:

  • The key to magnetic resonance imaging and nuclear magnetic resonance is producing enormous magnetic field to image the human body.
  • The electric resistance in materials makes it difficult to generate a large magnetic field which requires high electrical currents.
  • This is possible only by superconductors kept at ultra-low temperatures for which liquid helium is essential.

Magnetic Cooling technology and Helium:

  • Magnetic cooling technology could make fridges and air conditioners quieter, safer and more environmentally friendly.
  • Traditional cooling systems which use compressor-cooling technology will account for 13 percent of the entire world’s greenhouse gas emission by 2030.
  • Magnetic cooling requires extremely low temperatures which is possible with liquid helium.

Other Industrial applications:

  • Aerospace and defense technologies, high-tech manufacturing, rocket engine testing, welding, commercial diving, magnets in particle accelerators, the production of fiber optic cables and semiconductor chips found in cell phones

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