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Shapes of Molecules. Determined by number of valence electrons of the central atom 3-D shape a result of bonded pairs and lone pairs of electrons Use VSEPR theory (valence-shell-electron-pair repulsion. Using the VSEPR Model. 1. Draw the electron-dot structure Identify the central atom
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Shapes of Molecules • Determined by number of valence electrons of the central atom • 3-D shape a result of bonded pairs and lone pairs of electrons • Use VSEPR theory (valence-shell-electron-pair repulsion
Using the VSEPR Model 1. Draw the electron-dot structure • Identify the central atom • Count the total number of electron pairs around central atom • Predict the electron shape • Predict the shape of the molecule using the bonding atoms
Shapes of Molecules Number of electron pairs 2 (= negative charge clouds) Number of bonded atoms 2 Angle 180° Name of shape linear
BeCl2 Be 2 valence electrons .. .. : Cl : Be : Cl : .. .. .. .. : Cl Be Cl : linear, 180° .. ..
More Electron Pairs Electron Angle Bonded Name of Pairs Atoms Shape 3 120° 3 trigonal planar 3 120° 2 angular
BF3 B has 3 valence electrons 120° F trigonal planar B F F
SO2 S has 2 bonded atoms , 1 lone pair (electron cloud) 120°, angular .... .. :O:: S:O: S .. OO
More Electron Pairs Electron Angle Bonded Name of Pairs Atoms Shape 4 109° 4 tetrahedral 4 109° 3 pyramidal 4 109° 2 bent, angular
Tetrahedral CH4 4 electron Pairs, 4 bonded atoms, 109° H H C H C H H H H H
NH3 Pyramidal N has 4 electron pairs, 3 bonded H atoms Shape is called pyramidal .. H : N : H N .. H H H H ..
H2O Bent or Angular O has 4 electron pairs, 2 bonded H atoms Shape is called bent or angular, 109° .. : O : H O .. H H H .. ..
Learning Check Determine the molecular geometry of each of the following: A. CCl4 1) tetrahedral 2) pyramidal 3) angular B. SO3 1) trigonal planar 2) pyramidal 3) angular C. PCl3 1) trigonal planar 2) pyramidal 3) angular
Solution Determine the molecular geometry of each of the following: A. CCl4 1) tetrahedral B. SO3 1) trigonal planar C. PCl3 2) pyramidal