Here's why:

* Covalent bonds form when atoms share electrons to achieve a stable electron configuration.

* Hydrogen (H) has one electron in its outer shell and needs one more to become stable.

* Oxygen (O) has six electrons in its outer shell and needs two more to become stable.

* In H2O2, each oxygen atom shares one electron with each hydrogen atom and one electron with the other oxygen atom. This results in a single covalent bond between each hydrogen and oxygen atom and a single covalent bond between the two oxygen atoms.

Therefore, the structure of H2O2 can be visualized as:

H - O - O - H