Class 12 Chemistry MCQ – Solid State – Number of Atoms in a Unit Cell

This set of Class 12 Chemistry Chapter 1 Multiple Choice Questions & Answers (MCQs) focuses 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
View Answer

Answer: c
Explanation: 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
View Answer

Answer: a
Explanation: 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
View Answer

Answer: d
Explanation: 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.
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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
View Answer

Answer: c
Explanation: 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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