# 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

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

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

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.

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

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.

Sanfoundry Global Education & Learning Series – Chemistry – Class 12.

Note: Join free Sanfoundry classes at Telegram or Youtube

To practice all chapters and topics of class 12 Chemistry, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]