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Molecular Orbital Theory (MO – T)

Molecular Orbital Theory (MO – T). Atoms form bonds by sharing of electrons. Atoms can share 2, 4 or 6 electrons to form single, double or triple covalent bonds. It is actually impossible to determine the exact position of an electron, however, it is

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Molecular Orbital Theory (MO – T)

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  1. Molecular Orbital Theory (MO – T)

  2. Atoms form bonds by sharing of electrons. Atoms can share 2, 4 or 6 electrons to form single, double or triple covalent bonds. • It is actually impossible to determine the exact position of an electron, however, it is possible to calculate the probability of finding the electron at around any point around the nucleus using Schrondinger’s Wave Function (ψ). (VVI Wave fn to be included) • This equation can help predict and determine the spatial position of the electron around the nucleus, the energy and the geometry of the molecule. • A.O.’s combine to form M.O.’s that surround the molecule. Each M.O. can have 2 e with opposite spins. • When orbitals overlap, the electron density increases which in turn keeps the combining nuclei together. As a result Potential Energy of the bond decreases and this helps e to stay in a molecular bond rather than pushed back into 1s orbitals of individual atoms. • A Bonding M.O. can only be formed when orbitals of constituent atoms have the same energies, i.e., of the same phase. If A.O.’s have different phases, they interfere destructively and an Antibonding M.O. is formed.

  3. This type of M.O. can destabilize the molecule by decreasing the attraction between the atoms. Therefore, the number of Antibonding M.O. in a molecule should be less than the number of Bonding M.O.

  4. Principles of Molecular Orbital Theory (MO – T) When Atomic Orbitals (A.O.) of comparable energies and specific geometry combine, it forms Molecular Orbitals. Only Atomic Orbitals (A.O.) of comparable energies can combine. The number of A.O.’s determine the number of M.O.’s formed. If 2 A.O.’s combine, 2 M.O.’s will only be formed. The filling up of M.O.’s are identical as that of the filling up of shells following the same set of rules such as Aufbau Principle, Hund’s Multiplicity Rule and Pauli Exclusion Principle. One of the M.O. is known as Bonding Molecular Orbital that is of less energy than those of the constituent A.O.’s before bonding. The Antibonding Molecular Orbital has higher energy than the constituent A.O.’s before bonding.

  5. http://chemwiki.ucdavis.edu/Theoretical_Chemistry/Chemical_Bonding/Molecular_Orbital_Theory#http://chemwiki.ucdavis.edu/Theoretical_Chemistry/Chemical_Bonding/Molecular_Orbital_Theory# • http://chemwiki.ucdavis.edu/Theoretical_Chemistry/Chemical_Bonding/Molecular_Orbital_Theory/Bonding_and_antibonding_orbitals

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