Ionic Bond: An ionic bond is a type of chemical bond formed by the electrostatic attraction between oppositely charged ions, such as the positive calcium ion (Ca²⁺) and the negative fluoride ion (F⁻) in CaF₂.
Electronegativity: Electronegativity is a measure of an atom's ability to attract shared electrons in a chemical bond. The difference in electronegativity between calcium and fluorine is the driving force behind the formation of the ionic bond in CaF₂.
Coordination Number: The coordination number of an atom in a crystal structure is the number of nearest neighbor atoms surrounding it. In the CaF₂ crystal structure, each calcium ion is coordinated by eight fluoride ions, and each fluoride ion is coordinated by four calcium ions.