1. What is meant by the coordination number of an atom in a crystal lattice?
A.
The number of atoms present in one unit cell
B.
The number of nearest neighbouring atoms surrounding an atom
C.
The number of electrons in the atom
D.
The number of unit cells in the crystal
Correct Answer:
The number of nearest neighbouring atoms surrounding an atom
Explanation:
Coordination number is the number of nearest neighbouring atoms directly surrounding a particular atom in a crystal.
2. What is the coordination number of an atom in a simple cubic unit cell?
A.
4
B.
6
C.
8
D.
12
Correct Answer:
6
Explanation:
In a simple cubic structure, each atom has six nearest neighbours: one along each positive and negative direction of the three axes.
3. What is the coordination number of an atom in a body-centred cubic structure?
A.
4
B.
6
C.
8
D.
12
Correct Answer:
8
Explanation:
In a body-centred cubic structure, the atom at the body centre is surrounded by eight corner atoms at equal nearest-neighbour distance.
4. What is the coordination number of an atom in a face-centred cubic structure?
A.
4
B.
6
C.
8
D.
12
Correct Answer:
12
Explanation:
Each atom in a face-centred cubic structure has twelve nearest neighbouring atoms, so its coordination number is 12.
5. The coordination number of each atom in a hexagonal close-packed structure is:
A.
4
B.
6
C.
8
D.
12
Correct Answer:
12
Explanation:
In a hexagonal close-packed structure, every atom touches twelve nearest neighbours, giving a coordination number of 12.
6. Which crystal structure has the lowest coordination number among the following?
A.
Simple cubic
B.
Body-centred cubic
C.
Face-centred cubic
D.
Hexagonal close-packed
Correct Answer:
Simple cubic
Explanation:
Simple cubic has coordination number 6, which is lower than body-centred cubic (8) and the close-packed structures (12).
7. Which pair of crystal structures has the same coordination number?
A.
Simple cubic and body-centred cubic
B.
Body-centred cubic and face-centred cubic
C.
Face-centred cubic and hexagonal close-packed
D.
Simple cubic and hexagonal close-packed
Correct Answer:
Face-centred cubic and hexagonal close-packed
Explanation:
Both face-centred cubic and hexagonal close-packed structures have coordination number 12.
8. If each atom in a crystal has eight nearest neighbours, which structure is most likely present?
A.
Simple cubic
B.
Body-centred cubic
C.
Face-centred cubic
D.
Hexagonal close-packed
Correct Answer:
Body-centred cubic
Explanation:
A body-centred cubic structure is characterized by a coordination number of 8.
9. A crystal in which each atom is surrounded by six nearest neighbours has which coordination number?
A.
4
B.
6
C.
8
D.
12
Correct Answer:
6
Explanation:
The coordination number is the count of nearest neighbours, so six surrounding nearest neighbours give a coordination number of 6.
10. Which structure represents the maximum coordination number among the following common cubic and close-packed structures?
A.
Simple cubic
B.
Body-centred cubic
C.
Face-centred cubic
D.
Primitive tetragonal
Correct Answer:
Face-centred cubic
Explanation:
Face-centred cubic has coordination number 12, which is greater than the value 6 for simple cubic and 8 for body-centred cubic.
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