Assertion :If there is some gap between the conduction band and the valence band, electrons in the valence band all remain bound, and no free electrons are available in the conduction band. Reason: Some of the electrons in the valence band may gain external energy to cross trhe gap between the conduction band and the valence band.

Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

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Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

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Assertion is correct but Reason is incorrect

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Both Assertion and Reason are incorrect

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Solution

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
Band gap energy is the energy range in a solid where no electron states can exist. The band gap energy generally refers to the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. It is the energy(given externally) required to promote a valence electron bound to an atom to become a conduction electron, which is free to move within the crystal lattice and serve as a charge carrier to conduct electric current.
Hence both the statements are correct but the Reason is not correct explanation of Assertion.

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Similar questions

Q. Assertion :In some solids, the valence band is completely filled while the next higher band separated by an energy gap of few electrons-volts is completely empty. Reason: In insulators the energy band completely filled with electrons( the valence band) and above it is empty band (the conduction band)

Q. Assertion :We kn ow that a conduction band is an empty band just above the valence band into which electrons can pass. Reason: In conductors , the valence band is itself the conduction band.

Q. Assertion :If the temperature of a semiconductor is increased then its resistance decreases. Reason: The energy gap between conduction band and valence band is very small.

Q. Assertion :Intrinsic semiconductors are undoped Reason: Holes in the valence band are vacancies created by electrons that have been thermally excited to the conduction band

In the following questions a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct answer out of the following choices.

(a) Assertion and Reason both are correct statements an Reason is correct explanation for Assertion.

(b) Assertion and Reason both are correct satements but Reason is not correct explanation for Assertion.

(d) Assertion is wrong statement but Reason is correct statement.

Assertion (A) Semiconductors are solids with conductivities in the intermediate range from $10^{-} 6 - 10^{4} o h m^{-} 1 m^{-} 1$ .

Reason (R) Intermediate conductivity in semiconductor is due to partially filled valence band.

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