Question

The mass of unit cell of $Ca{F}_2$ (fluorite structure) corresponds to

• A. mass of $8C{a}^{++}$ ions and $4F^{-}$ ions
• B. mass of $4C{a}^{++}$ ions and $8F^{-}$ ions
• C. mass of $4C{a}^{++}$ ions and $4F^{-}$ ions
• D. mass of $1C{a}^{++}$ ions and $2F^{-}$ ions

Answer 1

Answer: (B)

In $Ca{F}_2$ (calcium fluorite) structure $1$-unit cell contains $4-C{a}^{2+}$ ions and $8F^{-}$ ions.
So, mass of unit cell of $Ca{F}_2$
= mass of $4C{a}^{2+}$ ions + mass of $8F^{-}$ ions