Which of the following gases is not inert gas?

A. Helium

B. Neon

C. Radon

D. Hydrogen

The correct answer is Hydrogen.

• Hydrogen is not an inert gas.

Key Points

• It comes under the S-block elements.
• S-Block:
  • It contains groups 1 and 2, i.e., hydrogen and alkali metals (Li, Na, K, Rb, Cs, Fr) and alkaline earth metals (Be, Mg, Ca, Sr, Ba, Ra).
  • The general electronic configuration of these elements is ns^0-2.
  • These elements are soft metals, electropositive.
• Inert Gases:
  • They belong to the 18th group of Periodic Table. For example, He, Ne, Ar, Kr, Xe, Rn.
  • Except for Rn, all inert gases are present in the atmosphere.
  • Argon is used in Arc. welding and electric bulbs.
  • Helium is light and non-inflammable so, used in a balloon, weather indicator, etc.
  • Neon is used in discharge tube glow light.

Additional Information

• The atom of hydrogen is the smallest and lightest.
• Hydrogen is the only atom in which neutrons are not present.
• Elements have the following order of abundance in the human body:
  • Oxygen >carbon> hydrogen > nitrogen.