VBT - Orbital Overlap and Bonding Orbital Overlap and...

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1 Valence Bond Theory Hybridization Helquist Emphasis & Highlights Orbital Overlap and Bonding • We think of covalent bonds forming through the sharing of electrons by adjacent atoms. • In such an approach this can only occur when orbitals on the two atoms overlap. • Each atom would contribute one valence electron to the covalent bond. • Increased overlap brings the electrons and nuclei closer together while simultaneously decreasing electron- electron repulsion. • However, if atoms get too close, the internuclear repulsion greatly raises the energy. Orbital Overlap and Bonding But it’s hard to imagine tetrahedral, trigonal bipyramidal, and other geometries arising from the atomic orbitals we recognize. Hybrid Orbitals • HYDROGEN and TERMINAL HALOGEN atoms can use their ATOMIC orbitals to form covalent bonds, as these atoms only need to form one single bond in molecules. • ALL OTHER ATOMS use HYBRID orbitals for bonding, according to Valence Bond Theory. Valence Bond Theory & Hybridization • Bonds are formed by overlap of orbitals. • Atomic orbitals on atoms can be mixed to create a new set of “hybrid” orbitals. • LCAO: The number of hybrid orbitals formed is always equal to the number of atomic orbitals that are mixed to create the hybrid set. • Hybrid orbitals sets are built by combining enough atomic orbitals (s, p and d) to accommodate the bonding groups and lone pairs on the atom. • The number of hybrid orbitals will always match the number of electron domains in the electron geometry of the atom. • The hybrid orbitals are directed at the terminal atoms, leading to better orbital overlap and stronger bonds between the atoms than would occur when using only atomic orbitals.
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2 Hybridization: 2 electron domains
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This note was uploaded on 02/16/2011 for the course CHEM 101 taught by Professor Naleway during the Spring '08 term at Loyola Chicago.

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VBT - Orbital Overlap and Bonding Orbital Overlap and...

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