When an oxygen atom forms chemical bonds with other atoms, it shares its orbitals through a process called orbital overlap. This occurs primarily with the outermost electrons, known as valence electrons.
Oxygen has six valence electrons, and its electron configuration is 1s^2 2s^2 2p^4. In order to achieve a stable configuration, oxygen tends to gain two electrons to complete its outermost energy level. Alternatively, it can share electrons with other atoms through covalent bonding.
Let's take the example of oxygen forming a covalent bond with another oxygen atom to create an oxygen molecule (O2). Each oxygen atom has two unpaired electrons in its 2p orbital that can participate in bonding. When two oxygen atoms come together, their 2p orbitals overlap to form molecular orbitals.
The process of orbital overlap involves the merging or mixing of atomic orbitals to form new orbitals that extend over both atoms. In the case of oxygen, the 2p orbitals overlap side by side, creating two molecular orbitals: a sigma (σ) bond and a pi (π) bond.
The sigma bond is formed by head-on overlap of the 2p orbitals along the internuclear axis. This sigma bond provides strong bonding between the oxygen atoms, with the electron density concentrated along the bond axis.
The pi bond, on the other hand, is formed by the sideways overlap of the 2p orbitals above and below the internuclear axis. This bond is weaker than the sigma bond and results in electron density that is above and below the plane of the molecule.
Overall, the sharing of electrons through orbital overlap allows oxygen atoms (or any other atoms) to form stable chemical bonds. This sharing of electrons helps satisfy the octet rule, where atoms strive to achieve a stable electron configuration with eight valence electrons.