Solid State

Since in NaCl type of structure 4 formula units form a cell. Number of formulas in cube shaped crystals
=‌

1.0

58.5

×6.02×1023
No. of unit cells present in a cubic crystal
=‌

P×a3×NA

M×Z

=‌

m×NA

m×Z

∴ units cells =‌

1.0×6.02×1023

58.5×4

=2.57×1021 unit cels.