Ionic Compound: An ionic compound is a chemical compound composed of ions held together by electrostatic forces. These compounds typically consist of metal cations and nonmetal anions.
Crystalline Structure: Crystalline structure refers to the orderly arrangement of atoms, ions, or molecules in a solid material. In CaF2, calcium and fluoride ions form a repeating pattern to create its crystalline structure.
Tooth Decay: Tooth decay is the process in which bacteria in the mouth produce acids that erode tooth enamel, leading to cavities. Calcium fluoride is used in toothpaste as it helps protect teeth from this decay.