Welcome to the NCERT Solutions for Class 12 Chemistry - Chapter The Solid State. This page offers a step-by-step solution to the specific question from Exercise 2, Question 17: . With detailed answers and explanations for each chapter, students can strengthen their understanding and prepare confidently for exams. Ideal for CBSE and other board students, this resource will simplify your study experience.
What is a semiconductor? Describe the two main types of semiconductors and contrast their conduction mechanism.
Semi- conductors are the solids that have properties intermediate between metals and insulators.They have only small difference in energy between the filled valence band and empty conduction band.The conductivity is also intermediate between that of a metal and an insulator and depends upon the number of electrons in the conduction band.
The semiconductors behaves in two types as
a) Intrinsic conduction
b) Extrinsic conduction
(a) Intrinsic conduction = pure silicon and germanium are poor conductors because they have network of four strong covalent bonds. But when electricity is provided to the crystals, the electrons moves leaving behind a positive charge or hole at the site of missing electron, as a result of which the crystal will now conduct electricity.
(b) Extrinsic conduction = here the conductivity of intrinsic conductors is increased by adding an appropriate amount of suitable impurity. This process is called doping. The impurities are of 2 types:
(1) Electron rich
(2) Electron deficient
(1) Electron rich impurity – here atoms with five valence electrons are added to the semiconductor, as a result of which four out of five electrons are used in formation of four covalent bonds with four neighbouring silicon atoms. The fifth electron is extra and becomes delocalised. These delocalised electrons increase the conductivity of doped silicon, hence increases the conductivity. This type of conductor is called n-type semiconductor.
(2) Electron deficient impurity – here an atom with three valence electrons are added to the semiconductor, as a result of which silicon or germanium atom are replaced by the impurity atom. The valence electrons of impurity will make bond with three atom but fourth atom remains free in the crystal of silicon or germanium, which is now available for conducting electricity. This type of conductor is called p-type semi- conductor.
The reaction between A and B is first order with respect to A and zero order with respect to B. Fill in the blanks in the following table:
| Experiment |
A/ mol L - 1 |
B/ mol L - 1 |
Initial rate/mol L - 1 min - 1 |
| I | 0.1 | 0.1 |
2.0 × 10 - 2 |
| II | -- | 0.2 |
4.0 × 10 - 2 |
| III | 0.4 | 0.4 | -- |
| IV | -- | 0.2 |
2.0 × 10 - 2 |
NCERT questions are designed to test your understanding of the concepts and theories discussed in the chapter. Here are some tips to help you answer NCERT questions effectively:
Stay updated with our latest educational content and study tips
Interest is one of the most significant ideas in maths and financial calculations. It is very common in banking, loan applications, investments, saving account and competitive exams. Simple Interest and Compound Interest make it easier to find out how much more is earned and/or paid on a principal during the period of time. These Interest … Read more
Read MoreIn 2026, students, professionals, and job seekers must have a high level of spoken English. Spoken English is a beginner level course to enhance learners’ communication skills in English, their pronunciation, vocabulary, grammar structure and confidence in speaking English fluently. Today, the emphasis of spoken English courses is placed on actual conversations, everyday speech practice … Read more
Read MoreArtificial Intelligence (AI) and Machine Learning (ML) are two of the most sought-after technologies in today’s digital era. Although these terms are often used together, they are not the same. Machine Learning is, in fact, a component of Artificial Intelligence that enables systems to learn and enhance on their own, without direct programming. AI is … Read more
Read MoreTime, Speed, and Distance are some of the most important concepts in mathematics and aptitude. These are the concepts which are used to calculate the speed of an object, time taken for an object to move and the distance traveled during the motion. Questions from this topic are frequently seen in School Tests, Competitive Tests, … Read more
Read MoreWelcome to the NCERT Solutions for Class 12 Chemistry - Chapter . This page offers a step-by-step solution to the specific question from Excercise 2 , Question 17: What is a semiconductor? Describe the two main types of semiconductors and contrast their conduction....
Add Comment