How do orbitals on individual atoms interact and change when covalent bonds form in molecules?

When covalent bonds form between atoms, their orbitals interact and change in a way that allows the atoms to share electrons. Let's break it down step by step:

1. Consider two individual atoms, each with their own set of orbitals. These orbitals are regions in space where there is a high probability of finding an electron.

2. When two atoms approach each other to form a covalent bond, their atomic orbitals can overlap. Overlapping occurs when the wave functions (describing the behavior of electrons) of the orbitals interact and merge together.

3. Depending on the type of overlap, there are two major types of covalent bonds that can form: sigma (σ) bonds and pi (π) bonds.

- Sigma (σ) bonds: This type of bond occurs when orbitals directly overlap along the internuclear axis (i.e., the line connecting the two atoms). The resulting bond is strong and allows for rotation around the bond axis.

- Pi (π) bonds: This type of bond occurs when orbitals overlap sideways, above and below the internuclear axis. Pi bonds are weaker than sigma bonds and restrict rotation around the bond axis.

4. As a result of the orbital overlap, the shared electrons are now located in the overlapping region between the nuclei of the bonded atoms. These shared electron pairs create a bond that holds the atoms together and helps stabilize the molecule.

5. When a covalent bond forms, the individual atoms' orbitals undergo changes. They can hybridize or mix to form new hybrid orbitals. This process enables the atoms to achieve a more stable electron configuration.

- Hybridization: Hybrid orbitals are formed when atomic orbitals combine, creating new orbitals with different shapes and energies. The number and types of hybrid orbitals depend on the number and arrangement of electron groups around the central atom. Examples of hybrid orbitals include sp, sp², sp³, and sp³d².

Overall, covalent bond formation involves the interaction and overlap of atomic orbitals, leading to the creation of strong sigma and weaker pi bonds. The resulting shared electron pairs contribute to the stability of the molecule, while the atoms' orbitals adapt and hybridize to accommodate the bonding.