In a covalent bond, the overlap of atomic orbitals occurs when the orbitals of two atoms come into close proximity and share electrons. This overlap allows the atoms to form a shared electron pair, resulting in the formation of a covalent bond between the atoms.
The extent of orbital overlap is crucial for the strength and stability of the covalent bond. The greater the overlap between the atomic orbitals, the stronger the bond. The overlap can occur between different types of atomic orbitals, such as s-s, p-p, s-p, or d-d orbitals, depending on the types of atoms involved and the geometry of the molecule.
The specific type of orbital overlap depends on the molecular geometry and the hybridization of the orbitals involved. For example, in a molecule with a linear geometry, the overlap typically involves the head-on interaction of two p orbitals. In molecules with tetrahedral geometry, such as methane (CH4), the overlap typically occurs between the sp3 hybrid orbitals of carbon and the 1s orbitals of the hydrogen atoms.
Overall, the overlap of atomic orbitals allows for the sharing of electrons between atoms, enabling the formation of covalent bonds and the stability of molecules.