Final answer:
BaO (barium oxide) has ionic bonds, formed between metallic barium, which loses electrons, and oxygen, which gains electrons, leading to a salt made up of Ba2+ and O2- ions.
Step-by-step explanation:
The substance that has ionic bonds among the options provided is BaO (barium oxide). In an ionic bond, one atom donates electrons to another to form ions that attract each other due to opposite charges. Barium is a metallic element with a low electronegativity, meaning it readily loses electrons to form positive ions (Ba2+), whereas oxygen has a high electronegativity and gains electrons to form negative ions (O2-). Thus, BaO consists of equal numbers of Ba2+ and O2- ions, held together by ionic bonds, forming a salt.
The other substances listed, such as O2 (oxygen molecule), OF2 (oxygen difluoride), and H2O (water), are composed of molecules that are held together by covalent bonds, where electrons are shared rather than transferred.