Question

Number of ion pairs in NaCl unit cell is:

• A. 2
• B. 4
• C. 6
• D. 8

Answer 1

The correct option is B 4

The chloride ions in NaCl are arranged in FCC.

So, cell content of chloride ions $=$ 4.

Sodium ions occupy the octahedral voids (i.e at body center and edge center).

$N{a}^{+}=12\times \frac{1}{4}+1=4$

So, each unit cell contains 4 pairs of NaCl.

Therefore, B is the correct answer.