Questions on Crystal Structures of Metals
20 Multiple-Choice Questions: Crystal Structures of Metals
Questions
1. What is the most densely packed metal crystal structure?
A) Body-centered cubic (BCC)
B) Face-centered cubic (FCC)
C) Hexagonal close-packed (HCP)
D) Simple cubic
E) Tetrahedral
2. Which crystal structure is exhibited by aluminum?
A) HCP
B) FCC
C) BCC
D) Orthorhombic
E) Monoclinic
3. Which of the following metals has a body-centered cubic (BCC) crystal structure?
A) Copper
B) Gold
C) Iron (at room temperature)
D) Zinc
E) Magnesium
4. The coordination number for atoms in an FCC structure is:
A) 6
B) 8
C) 10
D) 12
E) 14
5. What is the coordination number in a BCC structure?
A) 6
B) 8
C) 12
D) 10
E) 14
6. Which structure is NOT considered a common metallic crystal structure?
A) FCC
B) HCP
C) BCC
D) Tetrahedral
E) All are common
7. What is the arrangement of atoms in the HCP structure?
A) Linear
B) Tetrahedral
C) Cubic
D) Layered hexagonal
E) Orthorhombic
8. Which metal typically crystallizes in the HCP structure?
A) Iron
B) Silver
C) Zinc
D) Gold
E) Potassium
9. What is the number of atoms per unit cell in a face-centered cubic (FCC) structure?
A) 1
B) 2
C) 4
D) 6
E) 8
10. The crystal structure of gold is:
A) BCC
B) FCC
C) HCP
D) Tetragonal
E) Simple cubic
11. Which of the following metals transitions from BCC to FCC at higher temperatures?
A) Zinc
B) Iron
C) Aluminum
D) Copper
E) Nickel
12. How many atoms are in one unit cell of a BCC structure?
A) 1
B) 2
C) 3
D) 4
E) 5
13. Which packing structure has the highest packing efficiency?
A) FCC
B) BCC
C) HCP
D) Simple cubic
E) Diamond cubic
14. The packing efficiency of an FCC structure is approximately:
A) 52%
B) 60%
C) 68%
D) 74%
E) 82%
15. Why are FCC metals generally more ductile than BCC metals?
A) Weaker bonds
B) More slip systems
C) Lower melting point
D) Stronger bonds
E) Higher density
16. Which of these crystal structures has the fewest slip systems?
A) FCC
B) HCP
C) BCC
D) Simple cubic
E) Tetragonal
17. Which property is commonly associated with BCC metals?
A) High ductility
B) Low melting point
C) High hardness
D) High corrosion resistance
E) Transparent appearance
18. Which statement about FCC structures is true?
A) They are brittle
B) They have 6 slip systems
C) They have 12 atoms per unit cell
D) They allow easy dislocation movement
E) They occur only in nonmetals
19. Which crystal structure is NOT close-packed?
A) FCC
B) BCC
C) HCP
D) All are close-packed
E) FCC and HCP only
20. Which of the following metals is most likely to exhibit good formability due to its crystal structure?
A) Magnesium (HCP)
B) Chromium (BCC)
C) Copper (FCC)
D) Iron (BCC)
E) Beryllium (HCP)
Answers with Explanations
1. C) Hexagonal close-packed (HCP)
→ HCP and FCC have the highest packing efficiencies (~74%), but HCP is often slightly more densely packed.
2. B) FCC
→ Aluminum has a face-centered cubic structure.
3. C) Iron (at room temperature)
→ Alpha-iron is BCC at room temperature.
4. D) 12
→ FCC atoms are surrounded by 12 nearest neighbors.
5. B) 8
→ BCC structures have a coordination number of 8.
6. D) Tetrahedral
→ Not a typical metallic crystal structure.
7. D) Layered hexagonal
→ Atoms in HCP are arranged in hexagonal layers.
8. C) Zinc
→ Zinc typically forms HCP crystals.
9. C) 4
→ FCC unit cells contain 4 atoms total.
10. B) FCC
→ Gold has an FCC structure.
11. B) Iron
→ Iron transitions from BCC (α-Fe) to FCC (γ-Fe) at high temperature.
12. B) 2
→ BCC unit cell has 2 atoms: one at center, 1/8 of each corner.
13. A) FCC
→ FCC has highest packing efficiency (tied with HCP) at 74%.
14. D) 74%
→ FCC and HCP have the most efficient packing of atoms.
15. B) More slip systems
→ FCC has 12 slip systems, making deformation easier.
16. B) HCP
→ HCP has limited slip systems (usually 3), making it less ductile.
17. C) High hardness
→ BCC metals are usually harder and less ductile.
18. D) They allow easy dislocation movement
→ FCC structures are highly ductile due to many slip systems.
19. B) BCC
→ BCC is not close-packed; FCC and HCP are.
20. C) Copper (FCC)
→ FCC metals like copper are very ductile and easy to form.
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