Crystalline solids have an ordered and repetitive arrangement of particles in the three-dimensional space. Constituent particles may be atoms, ions or molecules. E.g. sodium chloride, quartz. Crystalline solids melt at a sharp and definite temperature. They are anisotropic, i.e. the properties such as refractive index and electrical conductivity differ in different directions. The unit cell is the smallest unit, which can be repeated in all directions to form a crystal lattice.

1. Find the radius of one atom in the unit cell, if the unit cell contains four metal atoms in the cubic crystal system. The edge length is 361 pm.

(a) 108 pm

(b) 80 pm

(c) 127 pm

(d) 40 pm

2. How many octahedral voids per atom are there in a cubic close-packed structure?

(a) 3

(b) 1

(c) 4

(d) 2

3. How many unit cells share a unit cell, in a face-centred cubic (fcc) lattice?

(a) 4

(b) 2

(c) 8

(d) 6

4. Which type of crystal is formed by a combination of a cation and anion?

(a) metallic

(b) ionic

(c) dipole-dipole

(d) covalent

5. Water is denser than ice due to

(a) induced dipole induced dipole interactions

(b) dipole-induced dipole interactions

(c) dipole-dipole interactions

(d) hydrogen bonding interactions

6. How many atoms are present in each unit cell of an fcc crystal?

(a) 8

(b) 6

(c) 5

(d) 4

7. The colour in solid alkali metal halides appears due to

(a) F-centres

(b) Interstitial positions

(c) Frenkel defect

(d) Schottky defect

8. What is the percentage of free space in a bcc (body centred cubic) unit cell?

(a) 28%

(b) 34%

(c) 32%

(d) 30%

9. Find the diameter of a metal atom in a face-centred cubic lattice, if the edge of the unit cell is 408 pm.

(a) 408 pm

(b) 288 pm

(c) 204 pm

(d) 144 pm

10. How many carbon atoms are present in a unit cell of a diamond?

(a) 1

(b) 6

(c) 8

(d) 4

Answer

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