* Covalent Bonding: Covalent bonding involves the sharing of electrons between atoms. Chlorine and oxygen are both nonmetals, and nonmetals tend to form covalent bonds.

* Electronegativity: Chlorine and oxygen have relatively similar electronegativity values. The difference isn't large enough to create the significant charge separation that defines an ionic bond.

* Molecular Structure: Chlorine oxide exists as a molecule, with the chlorine and oxygen atoms sharing electrons to form a bond.

In contrast, ionic compounds are formed when a metal and a nonmetal react, resulting in the transfer of electrons and the formation of charged ions.