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Names: Lab 2: Molecular Structure and VSEPR 1. For each molecule or ion: a. Column 1: Draw the Lewis dot structure. b. Column 2: Build the model. Use a black ball for the central atom and a stick with no ball on the end to represent a lone pair. For multiple bonds, use the thin, flexible sticks, one for each pair of electrons shared. If the molecule has lone pairs attached to the central atom, sketch the model in column 2. Otherwise, leave column 2 blank. Three-dimensional figures will need to be drawn with perspective so they don’t look flat. c. Column 3: Now, take out any lone pairs (so that your model only has atoms and bonds). This shows the molecular geometry or shape around the central atom. Sketch this model in column 3. (There should be no blanks in column 3.) Threedimensional figures will need to be drawn with perspective so they don’t look flat. d. Column 4: Write the name of the geometry of the molecule or ion (linear, bent, trigonal planar, trigonal pyramidal or tetrahedral). Refer to section 4.6 in your textbook. e. Column 5: Write the ideal bond angle. There are only three ideal angles, 180°, 120°, and 109.5°. f. Column 6: Write whether the molecule or ion is polar or nonpolar. Polarity depends on symmetry. Having different types of attached atoms decreases symmetry, so that bond polarities don’t cancel out. Having lone pairs also decreases symmetry, so that bond polarities don’t cancel out. When bond polarities cancel out, the molecular polarity is zero and the molecule is nonpolar. When bond polarities don’t cancel out, the molecular polarity is nonzero and the molecule is polar. Edited by Nick Buker 12/18/08 1 Column 1 Lewis Dot Structure Column 2 Sketch (with lone pairs) Column 3 Sketch (no lone pairs) Column 4 Molecular Geometry Column 5 Bond Angles Column 6 Polar or Nonpolar H2 O NH3 CH4 N2 CO2 Edited by Nick Buker 12/18/08 2 Column 1 Lewis Dot Structure PO4-3 Column 2 Sketch (with lone pairs) Column 3 Sketch (no lone pairs) Column 4 Molecular Geometry Column 5 Bond Angles Column 6 Polar or Nonpolar NH4+ SO4-2 C2CL2 C2H4 Edited by Nick Buker 12/18/08 3