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Chemical Bonding and Molecular Geometry. Valence-Shell Electron-Pair Repulsion (VSEPR) Theory. Electron pairs repel each other, both bond pairs and unshared (lone pairs) - Electron pairs assume orientations that minimize repulsions. Applying VSEPR Theory Draw a Lewis structure
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Valence-Shell Electron-Pair Repulsion (VSEPR) Theory • Electron pairsrepel each other, both bond pairs and unshared (lone pairs) • - Electron pairs assume orientations that minimize repulsions.
Applying VSEPR Theory • Draw a Lewis structure • Determine the number of electron groups around the central atom and identify them as being either bond pairs or lone pairs. • Establish the electrongroupgeometry around the central atom-linear,trigonal-planar,tetrahedral • Determine the moleculargeometry from the positions around the central atom occupied by the other atomic nuclei.
# of atoms bonded tocentral atom # lone pairs on central atom Arrangement ofelectron pairs Molecular Geometry linear linear B B Valence shell electron pair repulsion (VSEPR) model: Predict the geometry of the molecule from the repulsions between the electron (bonding and nonbonding) pairs. 2 0 10.1
0 lone pairs on central atom Cl Cl Be 2 atoms bonded to central atom 10.1
# lone pairs on central atom # of atoms bonded tocentral atom trigonal planar trigonal planar Arrangement ofelectron pairs Molecular Geometry VSEPR 2 0 linear linear 3 0 10.1
# of atoms bonded tocentral atom # lone pairs on central atom trigonal planar Arrangement ofelectron pairs Molecular Geometry bent VSEPR trigonal planar trigonal planar 3 0 2 1 10.1
# lone pairs on central atom trigonal planar trigonal planar # of atoms bonded tocentral atom 3 0 Arrangement ofelectron pairs Molecular Geometry tetrahedral tetrahedral VSEPR 0 linear linear 2 4 0 10.1
# lone pairs on central atom # of atoms bonded tocentral atom trigonal pyramidal tetrahedral Arrangement ofelectron pairs Molecular Geometry VSEPR 4 tetrahedral tetrahedral 0 1 3 10.1
Hybrid Atomic Orbitals(1931 - Linus Pauling) • Proposed that the outermost (valence) orbitals of an atom could be combined to form hybrid atomic orbitals. • Sigma bond( • The end-to-end overlapping of an s orbital with a p orbital to form a sp hybrid orbital. • Pi bond ( • ) - The side-to-side overlapping of two p orbitals. • Single bonds are made up of one sigma bond. • Double bonds are made up of one sigma bond and one pi bond. • Triple bonds are made up of one sigma bond and two pi bonds. • Hybridization - A mixture of two or more atomic orbitals.