Question

What do you understand by the fact that CaF₂ has 8 : 4 coordination?

Answer 1

The statement that CaF₂ has 8 : 4 coordination refers to the coordination numbers of the ions in its crystal structure. Each Ca²⁺ ion is surrounded by 8 F⁻ ions, meaning its coordination number is 8. Each F⁻ ion is surrounded by 4 Ca²⁺ ions, so its coordination number is 4. This type of coordination is characteristic of the fluorite structure (CaF₂), where the Ca²⁺ ions form a face-centred cubic (fcc) arrangement and the F⁻ ions occupy all the tetrahedral voids.