Which inert gas is used in double-glazed windows to fill the space between the panes?

The correct answer is Argon.

Key Points

• Argon is a chemical element with the atomic number 18.
  • It is a Nobel gas.
  • It is in group 18 of the periodic table.
  • Argon is the third most abundant gas in the Earth's atmosphere (0.094%)
  • Uses: Fluorescent Lightning, Gas Discharge Tubes, Fluorescent Glow Starters.

Additional Information

• Xenon
  • Xenon(Xe) gas is also known as stranger gas.
  • It is called 'STRANGER GAS' because the word 'XENON' means 'STRANGE' in Greek.
  • The noble gas Xenon possesses the highest melting point.
  • It was discovered by William Ramsay and Morris Travers in 1898.
  • It is more than 4.5 times heavier than air.
  • xenon is colorless, odorless, and tasteless.
  • It is used in instruments for radiation detection.
• Radon
  • Group 18 consists of six elements: helium, neon, argon, krypton, xenon and radon.
  • All these are gases and chemically unreactive.
  • They form very few compounds.
  • Because of this they are termed noble gases.
  • All the noble gases except radon occur in the atmosphere.
  • Xenon and radon are the rarest elements of the group.
  • Radon is obtained as a decay product of 226Ra.
• Helium
  • Helium is the 2nd most abundant element available in the universe. 
  • Helium symbol (He) considered as noble gas having Atomic Number 2. 
  • It is colorless, odourless, tasteless and non toxic.
  • Helium gas is used to inflate party balloons, scientific balloons and blimps etc.
  • Atomic mass of Helium is 4.002602 u.
  • Boiling point of Helium is -268.9 °C.