Question

In calcium fluoride, having the fluorite structure, the coordination numbers for calcium ion $(Ca^{2+})$ and fluoride ion $(F^-)$ are

• A. 4 and 2
• B. 6 and 6
• C. 8 and 4
• D. 4 and 8

Answer 1

The Correct Option is C

To solve this question, we need to understand the structure of calcium fluoride (CaF_2), which exhibits the fluorite structure. In this crystalline structure, different ions arrange themselves in a specific order that defines their coordination numbers.

1. The fluorite structure is a type of crystal structure common to many ionic compounds. In this arrangement, each calcium ion (Ca^{2+}) is surrounded by eight fluoride ions (F^-).
2. This arrangement results in the coordination number being 8 for the Ca^{2+} ions. Coordination number is defined as the number of opposite charges surrounding an ion.
3. Simultaneously, each fluoride ion (F^-) is surrounded by four calcium ions (Ca^{2+}), giving it a coordination number of 4.

Thus, in the fluorite structure of calcium fluoride (CaF_2), the coordination numbers for the calcium ion (Ca^{2+}) is 8, and for the fluoride ion (F^-) is 4.

Therefore, the correct answer is: 8 and 4.

This conclusion matches the correct option provided.