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Question
Assertion :Conductivity of silicon increases by doping it with group−15 elements. Reason: Doping means introduction of small amount of impurities like P,As or Bi into the pure crystal.
Assertion :Conductivity of silicon increases by doping it with group−15 elements. Reason: Doping means introduction of small amount of impurities like P,As or Bi into the pure crystal.
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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
When a silicon crystal is doped with a group 15 elements such as P,As,Sb or Bi the structure of the crystal lattice is left unchanged but an occasional atom with five valence electrons occupies a site that would normally be occupied by a silicon atom.
The foreign atom uses four of its electrons in covalent bonding but the remaining fifth electron becomes delocalized and is thus free to contribute to electrical conduction.
Thus, both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
Option B is the answer.
When a silicon crystal is doped with a group 15 elements such as P,As,Sb or Bi the structure of the crystal lattice is left unchanged but an occasional atom with five valence electrons occupies a site that would normally be occupied by a silicon atom.
The foreign atom uses four of its electrons in covalent bonding but the remaining fifth electron becomes delocalized and is thus free to contribute to electrical conduction.
Thus, both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
Option B is the answer.
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