In fluorite structure (CaF2)
Ca2+ ions are ccp and F- ions are present in all the tetrahedral voids
Ca2+ ions are ccp and F- ions are present in all the octahedral voids
Ca2+ ions are ccp and F- ions are present in all the octahedral voids & half of thetetrahedral voids
None
Ca2+ ions are ccp and F- ions are present in all the tetrahedral voids