One formula unit of calcium fluoride, represented as CaF2, consists of two different types of ions: calcium ions and fluoride ions. In this compound, there is one calcium ion (Ca2+) for every two fluoride ions (F–).
Specifically, the calcium ion carries a +2 positive charge, which allows it to bond with two negatively charged fluoride ions, each carrying a -1 charge. This charge balance is what stabilizes the compound. Overall, in a single formula unit of CaF2, the composition can be expressed as:
- 1 Calcium ion (Ca2+)
- 2 Fluoride ions (F–)
This 1:2 ratio is crucial for the formation of the ionic bond that characterizes calcium fluoride. Thus, the complete composition of one formula unit of CaF2 is:
1 Ca2+ + 2 F–