Question

In fluorite structure $\left(\right.CaF_{2})-$

• A. $Ca^{2 +}$ ions form ccp & $F^{-}$ ions are present in all the tetrahedral voids
• B. $Ca^{2 +}$ ions form ccp & $F^{-}$ ions are present in all the octahedral voids
• C. $Ca^{2 +}$ ions form ccp & $F^{-}$ ions are present in half of the octahedral voids and the rest half ions in the tetrahedral voids
• D. None

Answer 1

Answer: (A)

$Ca^{2 +}$ ions form ccp and $F^{-}$ ions are present in the tetrahedral voids. So, the no. of $Ca^{2 +}$ ions is 4 and no. of $F^{-}$ ions is 8.
So, the formula of the Calcium fluoride $Ca_{4}F_{8}$ or, the simplest formula of calcium fluoride is $CaF_{2}$ .