The total number of tetrahedral voids in the face centered unit cell is -
1. 6
2. 8
3. 10
4. 12
Same coordination number for cations and anions is present in:
1. | Cl^{-} ions form Fcc lattice and Na^{+} ions occupy all octahedral voids of the unit cell. |
2. | Ca^{2+} ions form Fcc lattice and F^{-} ions occupy all the eight tetrahedral voids of the unit cell. |
3. | O^{2-} ions form Fcc lattice and Na^{+} ions occupy all the eight tetrahedral voids of the unit cell. |
4. | S^{2-} ions form Fcc lattice and K^{+} ions go into alternate tetrahedral voids of the unit cell. |
Which of the following is not true about the ionic solids?
1. | Bigger ions form the close packed structure |
2. | Smaller ions occupy either the tetrahedral or‘the octahedral voids depending upon their size |
3. | Occupation of all the voids is not necessary |
4. | The fraction of octahedral or tetrahedral voids occupied depends upon the radii of the ions occupying the voids |
In the cubic close packing, the unit cell has ......... .
1. | 4 tetrahedral voids each of which is shared by four adjacent unit cells. |
2. | 4 tetrahedral voids within the unit cell. |
3. | 8 tetrahedral voids each of which is shared by four adjacent unit cells. |
4. | 8 tetrahedral voids within the unit cells. |
The edge lengths of the unit cells in terms of the radius of spheres constituting fcc, bcc, and simple cubic unit cells are respectively -
1. $2\sqrt{2\mathrm{r}},\frac{4\mathrm{r}}{\sqrt{3}},2\mathrm{r}$
2. $\frac{4\mathrm{r}}{\sqrt{3}},2\sqrt{2\mathrm{r}},2\mathrm{r}$
3. $2\mathrm{r},2\sqrt{2\mathrm{r}},\frac{4\mathrm{r}}{\sqrt{3}}$
4. $2\mathrm{r},\frac{4\mathrm{r}}{\sqrt{3}},2\sqrt{2\mathrm{r}}$
Which of the following is not true about the voids formed in a 3-dimensional hexagonal close-packed structure?
I. | A tetrahedral void is formed when a sphere of the second layer is present above the triangular void in the first layer |
II. | All the triangular voids are not covered by the spheres of the second layer |
III. | Tetrahedral voids are formed when the triangular voids in the second layer lie above the triangular voids in the first layer and the triangular shapes of these voids do not overlap |
IV. |
Octahedral voids are formed when the triangular voids in the second layer exactly overlap with similar voids in the first layer |
The correct choice among the given is -
1. (I, II)
2. (II, III)
3. (III, IV)
4. (I, III)
The number of tetrahedral voids per unit cell in NaCl crystal is -
I. 4
II. 8
III. Twice the number of octahedral voids
IV. Four times the number of octahedral voids.
The correct choice among the given is-
1. (I, II)
2. (II, III)
3. (III, IV)
4. (I, IV)
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 |
Codes
A | B | C | D | |
1. | 3 | 2 | 4 | 1 |
2. | 1 | 2 | 3 | 4 |
3. | 3 | 1 | 4 | 2 |
4. | 4 | 1 | 3 | 2 |
Select the correct option based on statements below:
Assertion (A): | Total number of octahedral voids present in the unit cell of cubic close packing including the one that is present at the body center, is four. |
Reason (R): | Besides the body center there is one octahedral void present at the center of each of the six faces of the unit cell and each of which is shared between two adjacent unit cells. |
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. | (A) is false but (R) is true. |