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JEE Main levelOne or more correct optionsDifficulty 2 of 3ss140

Which statements about the NaCl crystal structure are correct?

A $Cl X^{-}$ ions form a ccp lattice and $Na X^{+}$ ions occupy all octahedral voids.
BThere are 4 formula units per unit cell.
CThe coordination number of each ion is 6.
DThere are 2 $Na X^{+}$ ions per unit cell.

Answer: A, B, C

Cl X^{-}

:

8 \times \frac{1}{8} + 6 \times \frac{1}{2} = 4

.

Na X^{+}

: 12 edge centres

\times \frac{1}{4}

plus 1 body centre

= 4

. So

Z = 4

, not 2, and CN is 6:6.

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