Which of the following is correctly ordered according to the ascending order of band gap energy?

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  1. Silicon, Graphite, Diamond
  2. Graphite, Silicon, Diamond
  3. Silicon, Diamond, Graphite
  4. Diamond, Graphite, Silicon

Answer (Detailed Solution Below)

Option 2 : Graphite, Silicon, Diamond
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Detailed Solution

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CONCEPT:

  • Forbidden energy gap (ΔEg): The energy gap between the conduction band and valence band is known as the forbidden energy gap i.e.,

ΔEg = (C.B)min - (V.B)max

F1 P.Y Madhu 13.05.20 D9

  • No free electron is present in the forbidden energy gap.
  • The width of the forbidden energy gap depends upon the nature of the substance.
  • As the temperature increases, the forbidden energy gap decreases very slightly.

 

F1 P.Y Madhu 13.05.20 D11

  • In a conductor, the conduction band is partially filled and the valanced band is partially empty or when the conduction and valance bands overlap. When there is overlap electrons from the valence band can easily move into the conduction band

F1 P.Y Madhu 13.05.20 D12

  • In an insulator, there exists a large bandgap between the conduction band and valence band Eg (Eg > 3 eV). There are no electrons in the conduction band, and therefore no electrical conduction is possible.

F1 P.Y Madhu 13.05.20 D13

  • In semiconductors, there exists a finite but small band gap between the conduction band and valence band (Eg < 3 eV). Because of the small bandgap, at room temperature, some electrons from the valence band can acquire enough energy to cross the energy gap and enter the conduction band.
  • Therefore, the forbidden energy bandgap in conductors, semiconductors, and insulators are in the relation insulator > semiconductor > conductor.

 

Therefore, the correct order is Graphite, Silicon, Diamond

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