Covalent Bonding
Ionic bonds are characterized by a transfer of electrons between elements to form a stable compound. These bonds typically form in compounds consisting of a metal and a nonmetal, which are positively and negatively charged respectively.
Covalent bonds are characterized by a sharing of electrons between the elements in the compound. Covalent bonds are formed between nonmetals and in many inorganic compounds as well.
Metallic bonding, as the name suggests, is formed between metals.
Since phosphorus pentoxide consists of 4 phosphorus atoms and 10 oxygen atoms, and both of which are categorized as nonmetals, phosphorus pentoxide is therefore, bonded covalently.