Define covalent bonds according to quantum theory of valence bond theory (modern concept).
Answers
Valence bond theory:
The overlap of atomic orbits leads to the development of a chemical bond. Because of the overlap, electrons are located in the bond region. It describes the electronic structure of molecules.
Postulates:
· The overlap of two half-filled valence orbitals of two atoms of different types leads to covalent bond formation. It leads the stability of the molecule.
· If the atomic orbitals have more than one unpaired electron, more than one bond can be formed and electrons coupled in the valence shell cannot participate in the formation of such a bond.
· Based on the overlap pattern, two types of covalent bonds exist: sigma and pi. The covalent bond is formed by the side-overlapping of atomic orbitals is known as the pi bond, while the bond formed by atomic orbital overlapping along the inter-core axis is known as the sigma bond.
· Covalent bond is directional.