Here's why:
* Oxygen's electron configuration: Oxygen has 8 electrons, with 2 in its first shell and 6 in its second shell.
* Full outer shell: The second shell can hold up to 8 electrons.
* Valence electrons: Valence electrons are the electrons in the outermost shell, which are involved in bonding. Oxygen has 6 valence electrons.
To have a full outer shell, oxygen needs to gain two more electrons, bringing the total in its second shell to 8. This is why oxygen often forms two covalent bonds to achieve a stable octet.
