* Electrostatic Attraction: Calcium (Ca) is a metal and has a tendency to lose two electrons to form a positive ion (Ca²⁺). Chlorine (Cl) is a nonmetal and has a tendency to gain one electron to form a negative ion (Cl⁻). The strong electrostatic attraction between the positively charged calcium ions and the negatively charged chloride ions forms the ionic bond.

* Electronegativity Difference: The electronegativity difference between calcium (1.0) and chlorine (3.0) is large (2.0), indicating a transfer of electrons rather than sharing.

* Structure: Ionic compounds typically form crystalline structures due to the regular arrangement of ions in a lattice. Calcium chloride forms a crystal lattice with calcium ions surrounded by chloride ions.

In summary: The large electronegativity difference, the formation of ions, and the crystal structure all point towards an ionic bond in calcium chloride.