Chemistry Quiz for Schools on “Solid State – Number of Atoms in a Unit Cell”.
1. In primitive unit cubic cell, only _______ of an atom (or ion or molecule) belongs to a particular unit cell.
a) (frac{1}{4})th
b) (frac{1}{3})rd
c) (frac{1}{8})th
d) (frac{1}{2})nd
Answer: c
Clarification: In primitive unit cubic cell, each atom at the corner is shared between 8 adjacent unit cells. Thus, only (frac{1}{8})th of an atom (or ion or molecule) belongs to a particular unit cell.
2. The total number of atoms in one unit cell of primitive unit cubic cell is ______ atom(s).
a) 1
b) 8
c) 4
d) 2
Answer: a
Clarification: In primitive cubic unit cell, atoms are present only at the corner of the cell. Thus, in actual, only (frac{1}{8})th of an atom (or ion or molecule) belongs to a particular unit cell. Hence, the total number of atoms in primitive cubic unit cell = 8 × (frac{1}{8}) = 1 atom.
3. The total number of atoms in one unit cell of body-centered unit cubic cell is ______ atoms.
a) 4
b) 3
c) 8
d) 2
Answer: d
Clarification: In body-centered cubic unit cell, one atom is present at each of the corners and one atom at its body center.
• 8 corners × (frac{1}{8})th of an atom = 1
• 1 body-centered atom
Thus, the total number of atoms in body-centered cubic unit cell: 1+1=2 atoms.
4. The total number of atoms in one unit cell of face-centered unit cubic cell is ______ atoms.
a) 2
b) 6
c) 4
d) 8
Answer: c
Clarification: In face-centered cubic unit cell, atoms are present at each of the corners and at the centre of the face of the cube.
• 8 corners × (frac{1}{8})th of an atom = 1
• 6 faces × (frac{1}{2}) of an atom = 3
Thus, the total number of atoms in face-centered cubic unit cell: 1+3=4 atoms.
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