Q. No.The correct statement among the following is -
| 1. | Semiconductors have a small energy gap between the valence band and the conduction band. |
| 2. | Conductors have overlapped valence band and conduction band. |
| 3. | Insulators have a large energy gap between the valence band and conduction band. |
| 4. | All of the above. |
A compound that shows Schottky as well as Frenkel defect among the following is -
1. ZnS
2. AgBr
3. NaCl
4. AgCl
Schottky defect is observed in crystals when:
| 1. | Some cations move from their lattice site to interstitial sites. |
| 2. | Equal number of cations and anions are missing from the lattice. |
| 3. | Some lattice sites are occupied by electrons. |
| 4. | Some impurities are present in the lattice. |
NaCl is doped with 10−3 mol % of SrCl2. The number of cation vacancies post doping would be -
1. 4.022 × 108
2. 5.022 × 1018
3. 6.022 × 1018
4. 7.022 × 108
Match the items given in Column I with the items given in Column II.
| Column I | Column II |
| A. Mg in solid state | 1. p-type semiconductor |
| B. MgCl2 in molten state | 2. n-type semiconductor |
| C. Silicon with phosphorus | 3. Electrolytic conductors |
| D. Germanium with boron | 4. Electronic conductors |
Codes
| A | B | C | D | |
| 1. | 2 | 3 | 4 | 1 |
| 2. | 1 | 2 | 3 | 4 |
| 3. | 1 | 4 | 3 | 2 |
| 4. | 4 | 3 | 2 | 1 |
Schottky defect occurs mainly in electrovalent compounds where :
1. Positive ions have large sizes.
2. Negative ions have small sizes.
3. Positive and negative ions are of similar size.
4. Positive ions are big and negative ions are small.
Silicon doped with electron rich impurity forms -
1. p-type semiconductor.
2. n-type semiconductor.
3. Intrinsic semiconductor.
4. Insulator.
Select the correct option based on statements below:
| Assertion (A): | Due to Frenkel defect, the density of the crystalline solid decreases. |
| Reason (R): | In Frenkel defect cation and anion leave the crystal. |
| 1. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are true but (R) is not the correct explanation of (A). |
| 3. | (A) is true but (R) is false. |
| 4. | Both (A) and (R) are false. |
The appearance of colour in solid alkali metal halides is generally due to:
1. F-centres.
2. Schottky defect.
3. Frenkel defect.
4. Interstitial positions.
A defect that has an equal number of missing cations and anions is:
1. Schottky defect.
2. Frenkel defect.
3. Both (1) and (2)
4. None of the above.
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