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What do you understand by linear combination of atomic orbitals in MO theory . |
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Answer» SOLUTION :Linear combination of atomic orbitals : The WAVE functions for the molecular orbitals can be obtained by solving Schrodinger wave equation for the molecule. Since solving the Schrodinger equation is too complex , APPROXIMATION methods are used to obtain the wave function for molecular orbitals. The most common method is the linear combination of atomic orbitals (LCAO) . The atomicorbitals are represented by the wave function `Psi`. Let US consider two atomic orbitals represented by the wave function `Psi_(A)" and " Psi_(B)` with comparable energy, combines to form two molecular orbitals. One is bondingmolecular ORBITAL `(Psi_("bonding") )` and the other is antibonding molecular orbital `(Psi_("antibonding"))` . The wave functions for these two molecular orbitals can be obtained by the linear combination of the atomic orbitals `Psi_(A)" and "Psi_(B)` as below. `Psi_("bonding") = Psi_(A) + Psi_(B) ` `Psi_("antibonding") = Psi_(A) - Psi_(B) ` The formation of bonding molecular orbital can be considered as the result of constructive interference of the atomic orbitals and the formation of antibonding molecular orbital can be the result of the destructive interference of the atomic orbitals. The formation of the two molecular orbitals from two1s orbitals is shown below. Constructive interaction : The two 1s orbitals are in phase and have the same sign.  
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