Question

In calcium fluoride, having the fluorite structure, the coordination numbers for calcium ion (ca2+) and fluoride ion (f– ) are

Answer 1

In Caf2 structure ca2+ atoms are surrounded by 8 f-atoms and F- atoms are surrounded by 4 Ca2+ atoms.

so the the coordination number of calcium and fluoride ions are

8 and 4

Answer 2

Hey !!

In CaF₂, having fluorite structure, coordination of Ca²⁺ = 8 and that of F⁻ = 4

Each Ca²⁺ ion is surrounded by 8 F⁻ ions has a co-ordination number of 8 whereas each F⁻ ion is surrounded by 4 C²⁺ ions. Thus, this structure has 8 : 4 co-ordination.

       Each unit cell contain 4 Ca²⁺ ions and 8 F⁻ ions. This may be explained as follows:-

Ca²⁺ ions per unit cell = 8 × 1/8 ( from corners ) + 6 × 1/2 ( from face-centres) = 1 + 3 = 4

HOPE IT HELPS YOU !!