Presentation on theme: "Molecular Geometry VSEPR - Valence Shell Electron Pair Repulsion Theory. In small molecules, electrons and bonds are arranged as far apart as possible."— Presentation transcript:
Molecular Geometry VSEPR - Valence Shell Electron Pair Repulsion Theory. In small molecules, electrons and bonds are arranged as far apart as possible.
Molecular Geometry This allows for atoms to have 3-D shapes different from their shapes in 2-D (paper).
Molecular Geometry Linear – the bonds form a straight line. Example CO 2 Bond Angle 180⁰ [http://cwx.prenhall.com/bookbind/pubbooks/hillchem3/medialib/media_portfolio/text_images/CH10/FG10_02-02d.JPG]
Molecular Geometry Trigonal Planar– The central atom has only 3 bonds. Example: CH 2 O (Formaldehyde) Bond angle 120⁰ [http://wps.prenhall.com/wps/media/objects/476/488316/Instructo r_Resources/Chapter_10/FG10_00-66c.JPG]
Molecular Geometry Tetrahedral –The central atom has only 4 bonds Example: CH 4 (methane) Bond Angle 109.5⁰ [http://wps.prenhall.com/wps/media/object s/476/488316/Instructor_Resources/Chapt er_10/FG10_00-69d.JPG]
Polarity Showing Polarity “Minus” sign above the high electronegative atom. “Plus” sign over the other atom. Draw arrow from plus to minus. [http://cwx.prenhall.com/bookbind/pubbooks/hillchem3/medialib/media_portfolio/text_images/CH09/FG09_11-02.JPG]
Compound Polarity Draw a correct 2-D compound with arrows along each bond. Example: CH 4 CH H H H
Compound Polarity Then, check to see if any of the arrows cancel out. To do this think “tug of war” CH H H H
Compound Polarity If all arrows cancel out, the molecule is non-polar or covalent. If the arrows do not cancel out, the molecule is polar or polar-covalent.
Compound Polarity Remember: 3D shape determines 2D drawing. Example: H 2 O HHO H H O