PROBLEM SET 4

PROBLEM SET 4 - BONDING Atom-Atom Interactions When atoms...

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MSE 110 - U of A Atom-Atom Interactions BONDING •We have then developed simpler models that describe the types or extremes in bonding that have been observed: ionic, covalent, metallic . •Recognize that the actual bonding in a particular molecule may lie somewhere between these extremes or types. The orbitals in molecules and collections of atoms are still described by Schrodinger’s equation. The potential, V, must be modified to reflect several or many nuclei being present. The solutions are now orbitals that extend over the molecule, each orbital can still only hold two electrons. The actual solutions are very complex. 0 ) ( 8 2 2 2 2 = + ψ πψ V E h m x When atoms interact with each other (react) the atoms and their electrons rearrange themselves to achieve the lowest energy state. Lowest energy state maximizes the electrostatic interaction between the electrons and all the protonic cores (atom nucleis), the electrons try to get as close to the cores (on average) as possible.
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MSE 110 - U of A TYPES OF BONDING Covalent: Electron density lies mid-way between atom pairs (equally shared). Most evident in homonuclear bonding (same atoms) H-H Ionic: Electron density concentrated around one of atoms in pair (electron transfer). Most evident in heteronuclear bonding (different atoms) with large difference in electronegativity. H-F Metallic: Electron density spread over entire solid. Solid Molecule Diamond NaCl
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MSE 110 - U of A COVALENT BONDING Linear Combination of Atomic Orbitals (LCAO) •A bonding” MO is made by adding the two AO. When occupied, the electron density in this orbital is located between the two nuclei and electrostatically attracts them to strengthen the bond. An “antibonding” MO is made by subtracting the two AO. When occupied, the electron density lies away from the region between the two nuclei. This exposes the protonic cores of the atoms to each other and causes a repulsive effect to destabilize the bond in the molecule. .
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This note was uploaded on 10/06/2009 for the course MSE 110 taught by Professor Lucas during the Spring '08 term at Arizona.

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PROBLEM SET 4 - BONDING Atom-Atom Interactions When atoms...

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