* Ionic bonds form between a metal and a nonmetal. Calcium (Ca) is a metal, and oxygen (O) and hydrogen (H) are nonmetals.

* Calcium readily loses two electrons to become a positively charged ion (Ca²⁺).

* The hydroxide group (OH⁻) is formed when oxygen shares electrons with hydrogen, creating a negatively charged ion.

* Electrostatic attraction between the positively charged calcium ion and the negatively charged hydroxide ions holds the compound together.

Therefore, the strong electrostatic forces between the oppositely charged ions are responsible for the formation of ionic bonds in calcium hydroxide.