* Ionic Compounds: Formed by the electrostatic attraction between positively charged ions (cations) and negatively charged ions (anions).

* Sodium Hydroxide Formation: Sodium (Na) is a metal and readily loses an electron to form a positively charged sodium ion (Na+). Hydroxide (OH-) is a polyatomic ion with a negative charge. These oppositely charged ions come together to form the compound.

In short: The strong electrostatic forces between the Na+ and OH- ions are what define sodium hydroxide as an ionic compound.