Potassium and oxygen form an ionic bond. This is because potassium is a metal and oxygen is a nonmetal. Metals and nonmetals have very different electronegativities, which means that they have very different abilities to attract electrons. When a metal and a nonmetal bond, the metal atom donates electrons to the nonmetal atom. This creates a positive ion (the metal atom) and a negative ion (the nonmetal atom). The positive and negative ions are then attracted to each other, forming an ionic bond.