Molecular Orbital Theory

Molecular Orbital Theory - To see how we use these concepts...

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Molecular Orbital Theory The Lewis Structure approach provides an extremely simple method for determining the  electronic structure of many molecules. It is a bit simplistic, however, and does have  trouble predicting structures for a few molecules. Nevertheless, it gives a reasonable  structure for many molecules and its simplicity to use makes it a very useful tool for  chemists. A more general, but slightly more complicated approach is the  Molecular Orbital  Theory . This theory builds on the electron wave functions of Quantum Mechanics to  describe chemical bonding. To understand MO Theory let's first review constructive and  destructive interference of standing waves starting with the full constructive and  destructive interference that occurs when standing waves overlap completely. When standing waves only partially overlap we get partial constructive and destructive  interference.
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Unformatted text preview: To see how we use these concepts in Molecular Orbital Theory, let's start with H 2 , the simplest of all molecules. The 1s orbitals of the H-atom are standing waves of the electron wavefunction. In Molecular Orbital Theory we view the bonding of the two H-atoms as partial constructive interference between standing wavefunctions of the 1s orbitals. We can also have partial destructive interference. The energy of the H 2 molecule with the two electrons in the bonding orbital is lower by 435 kJ/mole than the combined energy of the two seperate H-atoms. On the other hand, the energy of the H 2 molecule with two electrons in the antibonding orbital is higher than two separate H-atoms. To show the relative energies we use diagrams like this: In the H 2 molecule, the bonding and anti-bonding orbitals are called sigma orbitals ( )....
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This note was uploaded on 11/22/2011 for the course CHEMISTRY CHM1025 taught by Professor Laurachoudry during the Fall '10 term at Broward College.

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Molecular Orbital Theory - To see how we use these concepts...

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