Explain difference between MOT And VBT ?
Answers
Difference Between Valence Bond Theory and Molecular Orbital Theory
Definition
Valence Bond Theory: Valence bond theory is a basic theory that is used to explain the chemical bonding of atoms in a molecule.
Molecular Orbital Theory: Molecular orbital theory explains the chemical bonding of a molecule using hypothetical molecular orbitals.
Molecular Orbitals
Valence Bond Theory: The valence bond theory does not give details about molecular orbitals. It explains the bonding of atomic orbitals.
Molecular Orbital Theory: The molecular orbital theory is developed based on the molecular orbitals.
Types of Orbitals
Valence Bond Theory: The valence bond theory describes hybrid orbitals.
Molecular Orbital Theory: The molecular orbital theory describes bonding molecular orbitals and antibonding molecular orbitals.
Hybridization
Valence Bond Theory: The valence bond theory explains the hybridization of molecular orbitals.
Molecular Orbital Theory: The molecular orbital theory does not explain about the hybridization of orbitals.
Conclusion
Bothe valence bond theory and molecular orbital theory are used to explain the chemical bonding between atoms in molecules. However, the valance bond theory cannot be used to explain the bonding in complex molecules. It is much suitable for diatomic molecules. But molecular orbital theory can be used to explain the bonding in any molecule. Therefore it has many advanced applications than the valence bond theory. This is the difference between valence bond theory and molecular orbital theory.
Answer:
Explanation:Valence bond theory was first proposed by W.Heitler and F. London in 1927 whereas molecular orbital theory was first proposed by F. Hund and R.S. Mulliken in 1932.
The valence bond theory defines the hybridization of molecular orbitals whereas the molecular theory does not define anything about hybridization of orbitals.
Valence bond theory can only be applied for diatomic molecules whereas molecular orbital theory can be applied on polyatomic molecules.
In valence bond theory, bonds are localized to two atoms and not molecules while in molecular orbital theory, bonds are localized to both two atoms and molecules.
Valence theory explains about molecules occupying atomic orbitals whereas molecular orbitals theory explains about the mixing of atomic orbitals when forming molecules.
In valence bond theory, resonance plays an important role whereas in molecular orbital theory, resonance does not play any role.
In valence bond theory, atoms which are involved in the bond formation, maintain their individual characteristic nature. In contrast, in molecular orbital theory, atomic orbitals which form molecular orbitals, do not retain their individual characteristic nature.
In valence bond theory, there is no explanation of paramagnetic character of oxygen whereas in molecular orbital theory there is an elaborate explanation of paramagnetic character of oxygen.
In valence bond theory, the resulting molecular orbital is obtained by the combination of two wave functions of two unpaired electrons. On the other hand, in molecular orbitals theory, formation of the molecular orbitals is based on the LCAO approximation method, whereby atomic orbitals corresponding of the valence shell of two, only takes part in the formation of molecular orbitals.
In valence bond theory, some of the valence electrons are represented as not shared and not involved in the formation of the molecule. On the contrary, in molecular orbital theory, all the electrons of the valence shell are represented as having taken part in the bonding.
Valence bond theory has simplicity and convenience especially in terms of calculations whereas molecular orbital theory is somehow complex and tedious especially in terms of calculations.