Oxygen forms a double bond with itself in the oxygen molecule (O₂).

Here's why:

* Valence Electrons: Oxygen has 6 valence electrons (electrons in its outermost shell). To achieve a stable octet (8 electrons), it needs to gain two more electrons.

* Sharing Electrons: In the oxygen molecule, each oxygen atom shares two of its valence electrons with the other oxygen atom. This creates a double bond, where each oxygen atom has a complete octet.

Here's a simple representation:

O = O

Each line represents a shared pair of electrons, making a total of four shared electrons, which form the double bond.