Here's why:

* Oxygen's electron configuration: Oxygen has 8 electrons total. Its electron configuration is 1s² 2s² 2p⁴.

* Valence electrons: The outermost shell (2s² 2p⁴) contains 6 valence electrons.

* Bonding: Oxygen typically forms two covalent bonds to achieve a stable octet (8 electrons) in its outer shell. These two bonds involve sharing two of its valence electrons with other atoms.

Therefore, oxygen has 6 bonding electrons: two used in each covalent bond.