In calcium fluoride, having the fluorite structure, the coordination numbers for calcium ion (Ca2+) and fluoride ion (F-) are
4 and 2
6 and 6
8 and 4
4 and 8
As we learnt in
No. of atoms(z) for face centered unit cell -
Lattice points: at corners and face centers of unit cell.
For face centered cubic (FCC), z=4.
- wherein
The calcium ions in occupy all corners and face centres of the cube. Each Ca atom is surrounded by 8 F atoms.
F atoms occupy all tetrahedral sites. Each F atom is surrounded by 4 Ca atoms.
Correct option is 3.
Option 1)
4 and 2
This option is incorrect.
Option 2)
6 and 6
This option is incorrect.
Option 3)
8 and 4
This option is correct.
Option 4)
4 and 8
This option is incorrect.