The Solid State
31913
How many molecules are there in the unit cell of sodium chloride
1 \(2\)
2 \(4\)
3 \(6\)
4 \(8\)
Explanation:
(b)In \(NaCl\) (rock salt) : Number of \(N{a^ + }\)ions \( = 12\) (at edge centers) \( \times \frac{1}{4} + 1\)(at body centre)\( \times 1 = 4\).
Number of \(C{l^ - }\)ions \( = 8\) (at corners)\( \times \frac{1}{8} + 6\) (at face centre) \( \times \frac{1}{2} = 4\).
Thus \(4\) formula units per unit cell.