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| 1. |
Determine the number of formula units of NaCl in the unit cell. NaCl is a face centred cubic crystal. See the diagram of the NaCl unit cell in the text. |
| Answer» SOLUTION :Either of `Na^+` or `CI^(-)` IONS may be chosen as the lattice points. Choosing `CL^(-)` ions (as shown in the text), the CUBE contains a `Cl^(-)`ion at the centre of each face as well as at the corners of the unit cell. There are `12 Na^+` ions at the centres of 12 edges and 1 `Na^(+)`ion at the centre of the unit cell. | |