Valence Bond theory explains covalent bond creation as well as the electronic structure of molecules. The theory thinks that electrons take up atomic orbitals of individual atoms inside a molecule and how the electrons of one atom are attracted to the nucleus of other atom. This attraction raises as the atoms approach each other until the atoms reach a minimum distance in which the electron density starts to cause repulsion among the two atoms.
The valence bond theory had been proposed by London and Heitler to describe the development of covalent bond quantitatively utilizing quantum mechanics. Afterwards, Linus Pauling enhanced this theory by adding the concept of hybridization.
The primary postulates of this theory are listed below:
A covalent bond is made by the overlapping of 2 half loaded valence atomic orbitals of two various atoms.
The electrons within the overlapping orbitals get confined and paired among the nuclei of two atoms.
The electron density between 2 bonded atoms raises because of overlapping. This confers stability to the molecule.
Higher the extent of overlapping, more powerful is the bond formed.
The direction of the covalent bond is along the location of overlapping of the atomic orbitals i.e., covalent bond is directional.
What is hybridization?
The intermixing of several pure atomic orbitals of the atom with nearly same energy to offer same number of identical and degenerate new kind of orbitals is called hybridization. The new orbitals created are also referred to as hybrid orbitals.
In chemistry, a valence electron is actually an electron that is related to an atom and that can take part in the development of a chemical bonding; in an individual covalent bond, each atoms in the bond contribute a single valence electron in order to make a shared set. The existence of valence electrons can easily determine the components chemical properties and whether it might bond with other elements: For a principal group element, a valence electron can only be in the outermost electron shell. In a transition metal, a valence electron also can be in an interior shell.
Such as an electron in an interior shell, a valence electron has a chance to release or absorb energy in the type of a photon. This loss or gain of energy can easily trigger an electron to jump (move) to some more outer shell or even get rid from its linked atom's valence shell; this is called atomic excitation. When an electron manages to lose energy (thereby causing a photon to be emitted), next it moves to a more interior shell.