×6.022×1023 molecules of NaCl 4 molecules of NaCl are present as Cl−present occupy fcc lattice =4 ions of Cl− occupy Na+octahedral site =4 ions of Na+ 1 unit cell contain 4 molecules of NaCl 1 molecule contain
1
4
unit cell.
1
58.5
×6.022×1023 molecule contains =
1
58.5
×
6.022×1023
4
unit cell Thus, 1 g of NaCl contain =2.57×1021 unit cell.