How many molecules are there in the unit cell of sodium chloride?

Question

How many molecules are there in the unit cell of sodium chloride? (A) 2 (B) 6 (C) 4 (D) 8

Tardigrade Admin · Accepted Answer

In NaCl (rock salt): Number of Na+ ions = 12 (at edge centers)× (1/4) +1(at body centre) × 1 = 4. Number of Cl- ions = 8 (at comers) × (1/8) +6 (at face centre) × (1/2) = 4 . Thus 4 formula units per unit cell.

Q. How many molecules are there in the unit cell of sodium chloride?

$2$

$6$

$4$

$8$

In $N a Cl$ (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 comers) $\times \frac{1}{8}$
$+ 6$ (at face centre) $\times \frac{1}{2} = 4$ .
Thus $4$ formula units per unit cell.

Q. How many molecules are there in the unit cell of sodium chloride?

2

6

4

8

In NaCl (rock salt): Number of Na+ ions =12 (at edge centers)×41​ +1(at body centre) ×1=4. Number of Cl− ions =8 (at comers) ×81​ +6 (at face centre) ×21​=4 . Thus 4 formula units per unit cell.

$2$

$6$

$4$

$8$

In $N a Cl$ (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 comers) $\times \frac{1}{8}$
$+ 6$ (at face centre) $\times \frac{1}{2} = 4$ .
Thus $4$ formula units per unit cell.