Which of the following conditions favours the existence of a substance in the solid state?
Which of the following is not a characteristic of a crystalline solid?
Which of the following is an amorphous solid?
Which of the following arrangements shows schematic alignment of magnetic moments of antiferromagnetic substances?
Which of the following is true about the value of refractive index of quartz glass?
Which of the following statement is not true about amorphous solids?
The sharp melting point of crystalline solids is due to ..........
Iodine molecules are held in the crystals lattice by ...........
Which of the following is a network solid?
Which of the following solids is not an electrical conductor?
1. $\mathrm{Mg}(\mathrm{s})$
2. TiO (s)
3. $\mathrm{I}_2$ (s)
4. $\mathrm{H}_2 \mathrm{O}(\mathrm{s})$
Which of the following is not the characteristic of ionic solids?
Graphite is a good conductor of electricity due to the presence of ...........
Which of the following oxides behaves as conductor or insulator depending upon temperature?
Which of the following oxides shows electrical properties like metals?
The lattice site in a pure crystal cannot be occupied by ........... .
Graphite cannot be classified as .......... .
Cations are present in the interstitial sites in ......... .
Schottky defect is observed in crystals when ............ .
Which of the following is true about the charge acquired by p - type semiconductors?
To get a n-type semiconductor from silicon, it should be doped with a substance with valency ............. .
The total number of tetrahedral voids in the face centred unit cell is .......... .
Which of the following point defects are shown by $\mathrm{AgBr}(\mathrm{s})$ crystals?
1. Schottky defect
2. Frenkel defect
3. Metal excess defect
4. Metal deficiency defect
In which pair most efficient packing is present?
The percentage of empty space in a body centred cubic arrangement is ........... .
Which of the following statement is not true about the hexagonal close packing?
In which of the following structures coordination number for cations and anions in the packed structure will be same?
What is the coordination number in a square close packed structure in two dimensions?
Which kind of defects are introduced by doping?
Silicon doped with electron rich impurity forms ............ .
Which of the following statements is not true?
Which of the following is not true about the ionic solids?
A ferromagnetic substance becomes a permanent magnet when it is placed in a magnetic field because .......... .
The correct order of the packing efficiency in different types of unit cells is ............ .
Which of the following defects is also known as dislocation defect?
In the cubic close packing, the unit cell has ............. .
The edge lengths of the unit cells in terms of the radius of spheres constituting fcc, bcc and simple cubic unit cells are respectively ............. .
Which of the following represents correct order of conductivity in solids?
Assertion (A) The total number of atoms present in a simple cubic unit cell is one.
Reason (R) Simple cubic unit cell has atoms at its corners, each of which is shared between eight adjacent unit cells.
Assertion (A) Graphite is a good conductor of electricity however diamond belongs to the category of insulators.
Reason (R) Graphite is soft in nature on the other hand diamond is very hard and brittle.
Assertion (A) Total number of octahedral voids present in unit cell of cubic close packing including the one that is present at the body centre, is four.
Reason (R) Besides the body centre there is one octahedral void present at the centre of each of the six faces of the unit cell and each of which is shared between two adjacent unit cells.
Assertion (A) The packing efficiency is maximum for the fcc structure.
Reason (R) The coordination number is 12 in fcc structures.
Assertion (A) Semiconductors are solids with conductivities in the intermediate range from $10^{-6}-10^4 \mathrm{ohm}^{-1} \mathrm{~m}^{-1}$.
Reason (R) Intermediate conductivity in semiconductor is due to partially filled valence band.
Which of the following is not true about the voids formed in 3 dimensional hexagonal close packed structure?
The value of magnetic moment is zero in the case of antiferromagnetic substances because the domains ........... .
Which of the following statements are not true?
Which of the following statements are true about metals?
Under the influence of electric field, which of the following statement is true about the movement of electrons and holes in a p-type semiconductor?
Which of the following statements are true about semiconductors?
An excess of potassium ions makes KCl crystals appear violet or lilac in colour since .............. .
The number of tetrahedral voids per unit cell in NaCl crystal is
Amorphous solids can also be called ............ .
A perfect crystal of silicon (fig) is doped with some elements as given in the options. Which of these options shows n-type semiconductors?
Which of the following statements are correct?
Which of the following features are not shown by quartz glass?
Which of the following cannot be regarded as molecular solid?
In which of the following arrangements octahedral voids are formed?
Frenkel defect is also known as ........... .
Which of the following defects decrease the density?
Why are liquids and gases categorised as fluids?
Why are solids incompressible?
Inspite of long range order in the arrangement of particles why are the crystals usually not perfect?
Why does table salt, NaCl sometimes appear yellow in colour?
Why is $\mathrm{FeO}(\mathrm{s})$ not formed in stoichiometric composition?
Why does white Zn 0 (s) becomes yellow upon heating?
Why does the electrical conductivity of semiconductors increase with rise in temperature?
Explain why does conductivity of germanium crystals increase on doping with galium?
In a compound, nitrogen atoms $(\mathrm{N})$ make cubic close packed lattic and metal atoms (M) occupy one-third of the tetrahedral voids present. Determine the formula of the compound formed by M and N ?
Under which situations can an amorphous substance change to crystalline form?
Match the defects given in Column I with the statements in given Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | Simple vacancy defect | 1. | Shown by non-ionic solids and increases density of the solid |
| B. | Simple interstitial defect | 2. | Shown by ionic solids and decreases density of the solid |
| C. | Frenkel defect | 3. | Shown by non-ionic solids and density of the solid decreases |
| D. | Schottky defect | 4. | Shown by ionic solids and density of the solid remains the same |
Match the type of unit cell given in Column I with the features given in Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | Primitive cubic unit cell | 1. | Each of three perpendicular edges compulsorily have the different edge length i.e., $a\ne b \ne c$ |
| B. | Body centred cubic unit cell | 2. | Number of atoms per unit cell is one |
| C. | Face centred cubic unit cell | 3. | Each of the three perpendicular edges compulsorily have the same edge length i.e., $a=b=c$ |
| D. | End centred orthorhombic unit cell | 4. | In addition to the contribution from the corner atoms the number of atoms present in a unit cell is one |
| 5. | In addition to the contribution from the corner atoms the number of atoms present in a unit cell is three |
Match the types of defect given in Column I with the statement given in Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | Impurity defect | 1. | NaCl with anionic sites called F-centres |
| B. | Metal excess defect | 2. | FeO with Fe$^{3+}$ |
| C. | Metal deficiency defect | 3. | NaCl with Sr$^{2+}$ and some cationic sites vacant |
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. | MgCl$_2$ in molten state | 2. | n-type semiconductor |
| C. | Silicon with phosphorus | 3. | Electrolytic conductors |
| D. | Germanium with boron | 4. | Electronic conductors |
Match the type of packing given in Column I with the items given in Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | Square close packing in two dimensions | 1. | Triangular voids |
| B. | Hexagonal close packing in two dimensions | 2. | Pattern of spheres is repeated in every fourth layer |
| C. | Hexagonal close packing in three dimensions | 3. | Coordination number = 4 |
| D. | Cubic close packing in three dimensions | 4. | Pattern of sphere is repeated in alternate layers |
With the help of a labelled diagram show that there are four octahedral voids per unit cell in a cubic close packed structure.
Show that in a cubic close packed structure, eight tetrahedral voids are present per unit cell.
How does the doping increase the conductivity of semiconductors?
A sample of ferrous oxide has actual formula $\mathrm{Fe}_{0.93} \mathrm{O}_{1.00}$. In this sample, what fraction of metal ions are $\mathrm{Fe}^{2+}$ ions? What type of non-stoichiometric defect is present in this sample?