1. Which of the following axis system is being satisfied by monoclinic crystal system?
a) a = b = c, α = β = 90o ≠ ϒ
b) a ≠ b = c, α = β = ϒ = 90o
c) a ≠ b ≠ c, α = β = 90o ≠ ϒ
d) a = b = c, α ≠ β = ϒ = 90o
Explanation: Monoclinic have all sides unequal and two angles equal to 90o.
2. Which of the following axis system is being satisfied by triclinic crystal system?
a) a = b = c, α = β = ϒ = 90o
b) a ≠ b = c, α = β = ϒ = 90o
c) a ≠ b ≠ c, α ≠ β ≠ ϒ ≠ 90o
d) a = b = c, α ≠ β = ϒ = 90o
Explanation: Triclinic structures have all sides unequal and all angles are also unequal.
3. Which one of the following is most symmetrical?
a) Simple cubic cell
b) Hexagonal
c) Triclinic
d) Tetragonal
Explanation: In triclinic crystal system, we observe all the sides and angle to equal to each other (a = b = c and α = β = γ = 90o), thus giving highest symmetry (four 3-fold symmetry) among all 7 Bravais Lattices.
4. Which one of the following is least symmetrical?
a) Tetragonal
b) Simple cubic
c) Triclinic
d) Tetragonal
Explanation: In triclinic crystal system, we observe all the sides and angle to unequal to each other (a ≠ b ≠ c and α ≠ β ≠ γ ≠ 90o), thus giving least symmetry (1-fold symmetry) among all 7 Bravais Lattices.
5. What is the coordination number of a simple cubic (SC) unit cell?
a) 4
b) 6
c) 8
d) 2
Explanation: There are six nearest neighbouring atoms for every atom in a simple cubic (SC) unit cell, in other words, every atom in a SC unit cell is surrounded by 6 other atoms, thus coordination number of SC unit cell is is 6.
6. What is the coordination number of a face centered cubic (FCC) unit cell?
a) 4
b) 6
c) 8
d) 12
Explanation: In an FCC structure, there are eight atoms, one atom each at the corner of the unit cell and one atom at the centre of each face. For any corner atom of the unit cell, the nearest atoms are face-centred atoms. Thus, the coordination number for an FCC structure = 4 centre atoms below the horizonal plane + 4 centre atoms above the horizontal plane + 4 centre atoms on the horizonal plane.
Hence, the coordination number for an FCC structure is 4 + 4 + 4 = 12.
7. What is the coordination number of body centered cubic unit cell?
a) 4
b) 6
c) 8
d) 2
Explanation: For any corner atom of the BCC unit cell, the nearest atoms are the body centred atoms. There are eight-unit cells in neighbours with body-centered atoms. Hence, the coordination number for a BCC cubic unit cell is 8.
8. Effective number of atoms in a simple cubic (SC) unit cell is equal to ___________
a) 4
b) 1
c) 8
d) 2
Explanation: Total number of atoms at corners = 8 and each corner atom is shared by total 8-unit cells. Thus, effective number of atoms in an SC unit cell: 8 × 8⁄8 = 1.
9. Effective number of atoms in a face centered cubic (FCC) unit cell is equal to ________
a) 4
b) 1
c) 8
d) 2
Explanation: In an FCC unit cell, there are eight atoms: one at each corner of the cube and six face centered atoms of the six planes of the cube. As corner atoms are shared by eight adjacent cubes and the face centered atoms by two adjacent unit cells, total effective number of atoms in an FCC unit cell will be 4.
10. Effective number of atoms in a body centered cubic (BCC) unit cell is equal to _____________
a) 4
b) 6
c) 1
d) 2
Explanation: The unit cell of a cube contains eight atoms at the corners, which are shared by the eight adjoining cubes and one atom at the centre of the cube.
8 atoms at the corner: (8×1⁄8) = 1 atom + 1 centre atom in the unit cell, So, there are “2” effective number of atoms in a BCC unit cell.