This set of Engineering Materials & Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Types of Solids, Crystal Structures and Lattices”.
1. Lead is a metallic crystal having a _______ structure.
a) FCC
b) BCC
c) HCP
d) TCP
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Explanation: Crystalline solids are classified as either metallic or non-metallic. Pb, along with Cu, Ag, Al, and Ni, has a face-centered cubic structure.
2. Which of the following has a HCP crystal structure?
a) W
b) Mo
c) Cr
d) Zr
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Explanation: Crystalline solids are classified as either metallic or non-metallic. W, Mo, and Cr are examples of the body-centered cubic structure of crystals. The HCP structure is found in Mg, Zn, Ti, Cd, Zr, and others.
3. Amorphous solids have _______ structure.
a) Regular
b) Linear
c) Irregular
d) Dendritic
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Explanation: Materials in which the molecule is the basic structural solid and has an irregular structure is known as amorphous solid. Crystalline solids, on the other hand, usually are arranged in a regular manner.
4. At ________ iron changes its BCC structure to FCC.
a) 308oC
b) 568oC
c) 771oC
d) 906oC
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Explanation: Similar to metallic crystals, a few non-metallic crystals also change form due to temperature and pressure differences. This process is termed as polymorphism. Iron changes from BCC at room temperature to FCC form at 906oC.
5. At room temperature, tin is formed into _________
a) Gray tin
b) White tin
c) Red tin
d) Yellow tin
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Explanation: Similar to metallic crystals, a few non-metallic crystals also change form due to temperature and pressure differences. Tin crystallizes in a non-metallic diamond structure (gray tin) at low temperatures. At room temperature, it forms a metallic structure (white tin).
6. Which of the following is a property of non-metallic crystals?
a) Highly ductile
b) Less brittle
c) Low electrical conductivity
d) FCC structure
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Explanation: Non-metallic crystals are less ductile and have low electrical conductivity. On the other hand, metallic crystals are differing since they are more ductile and have high electrical conductivity.
7. Which of the following is not an amorphous material?
a) Glass
b) Plastics
c) Lead
d) Rubbers
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Explanation: Materials in which the molecule is the basic structural solid and has an irregular structure are known as amorphous solid. Most amorphous materials are polymers such as plastics and rubbers. The most common amorphous material is glass.
8. The crystal lattice has a _________ arrangement.
a) One-dimensional
b) Two-dimensional
c) Three-dimensional
d) Four-dimensional
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Explanation: Lattice is defined as the regular geometrical arrangement of points in crystal space. Space or crystal lattice is a three-dimensional network of imaginary lines connecting the atoms.
9. The smallest portion of the lattice is known as __________
a) Lattice structure
b) Lattice point
c) Bravais crystal
d) Unit cell
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Explanation: Lattice is defined as the regular geometrical arrangement of points in crystal space. The unit cell is the smallest portion of the lattice, which when repeated in all directions gives rise to a lattice structure.
10. Bravais lattice consists of __________ space lattices.
a) Eleven
b) Twelve
c) Thirteen
d) Fourteen
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Explanation: There are fourteen ways in which points can be arranged in a space so that each has identical surroundings. These fourteen space lattices constitute the Bravais space lattices.
11. A unit cell that contains lattice points only at the corners is known as _________
a) Primitive unit cell
b) Secondary unit cell
c) Layered unit cell
d) Derived unit cell
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Explanation: If a unit cell chosen contains lattice points only at its corners, it is called a primitive or simple unit cell. It contains only one lattice point since each point at the eight corners is shared equally with adjacent unit cells.
12. The axial relationship of a monoclinic crystal system is given as ___________
a) a = b = c
b) a = b ≠ c
c) a ≠ b = c
d) a ≠ b ≠ c
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Explanation: The crystal system is a format by which crystal structures are classified. Each crystal system is defined by the relationship between edge lengths a, b, and c. For monoclinic, orthorhombic, and triclinic systems, the axial relationship is given by a ≠ b ≠ c.
13. The axial relationship of a rhombohedral crystal system is given as ___________
a) a = b = c
b) a = b ≠ c
c) a ≠ b = c
d) a ≠ b ≠ c
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Explanation: The crystal system is a format by which crystal structures are classified. Each crystal system is defined by the relationship between edge lengths a, b, and c. For cubic and rhombohedral systems, the axial relationship is given by a = b = c.
14. The interracial angles of a hexagonal crystal system are given by __________
a) α = β = ϒ = 90o
b) α = β = 90o ϒ = 120o
c) α = β = ϒ ≠ 90o
d) α ≠ β ≠ ϒ ≠ 90o
View Answer
Explanation: The crystal system is a system by which crystal structures are classified. Each crystal system is defined by the relationship between edge lengths a, b, and c and interaxial angles α, β, and ϒ. For hexagonal system, the interaxial angles are given by α = β = 90o ϒ = 120o.
15. The interracial angles of a triclinic crystal system are given by __________
a) α = β = ϒ = 90o
b) α = β = 90o ϒ = 120o
c) α = β = ϒ ≠ 90o
d) α ≠ β ≠ ϒ ≠ 90o
View Answer
Explanation: The crystal system is a system by which crystal structures are classified. Each crystal system is defined by the relationship between edge lengths a, b, and c and interaxial angles α, β, and ϒ. For the triclinic system, the interaxial angles are given by α ≠ β ≠ ϒ ≠ 90o.
16. What is the atomic radius of a BCC crystal structure?
a) a/2
b) a/4
c) a√2/4
d) a√3/4
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Explanation: Atomic radius is defined as half the distance between the centers of two neighboring atoms. The atomic radius of a simple cube and HCP is a/2 respectively, whereas it is a√2/4 and a√3/4 for FCC and BCC respectively.
17. What is the coordination number of a simple cubic structure?
a) 6
b) 8
c) 10
d) 12
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Explanation: Coordination number is defined as the number of nearest neighboring atoms in crystals. The coordination number for the simple cubic structure is 6, whereas it is 8 and 12 for BCC and FCC respectively.
18. What is the atomic packing factor of BCC structure?
a) 0.54
b) 0.68
c) 0.74
d) 0.96
View Answer
Explanation: The density of packing in a crystal is determined using the atomic packing factor (APF). The APF of FCC and HCP structures is 0.74, and 0.54 for simple cubic structure, whereas it is 0.68 for BCC structure.
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