Here's why:

* Oxygen has six valence electrons. Valence electrons are the outermost electrons involved in bonding.

* Oxygen needs two more electrons to complete its octet. An octet is a stable configuration with eight electrons in its outer shell.

* Oxygen achieves this by forming two covalent bonds. Covalent bonds involve sharing electrons between atoms.

Let me know if you'd like to know more about covalent bonding or other aspects of oxygen's chemistry!