Unit3Day3 LaBrake Thursday October 17 2013 8 13 AM Vanden Bout LaBrake CH301 How Can a Molecule Have Shape Take a Closer Look at Shape Bonding UNIT 3 Day 3 CH301 Vanden Bout LaBrake Fall 2013 Important Information LM21 DUE Tue 9AM HW 7 DUE Tue 9AM Laude LM Lecture 12 CH301 Vanden Bout LaBrake Spring 2013 Unit3Day3 LaBrake Page 1 What are we going to learn today Understand Predict Molecular Polarity Based on Shape Understand Bonding Theory Supporting Experimentally Determined Shapes VB Theory and bonds CH301 Vanden Bout LaBrake Fall 2013 Quiz CLICKER QUESTION 1 Given a tetrahedral electronic geometry which of the following molecular geometries is not possible a Bent b Trigonal pyramidal c Tetrahedral d Trigonal planar CH301 Vanden Bout LaBrake Fall 2013 Unit3Day3 LaBrake Page 2 REVIEW LEARNING MODULE 20 Qr CH4 your left sector NH3 center sector H2O your right sector Make a model of one of these molecules Use different colored clay balls for the different elements in compound CH301 Vanden Bout LaBrake Fall 2013 Are the bonds polar Are the molecules polar Is there a dipole moment Are the questions Is the molecule polar and Is does the molecule have a dipole moment the same question Unit3Day3 LaBrake Page 3 Are the bonds polar Are the molecules polar Is there a dipole moment Are the questions Is the molecule polar and Is does the molecule have a dipole moment the same question the same question Have a little moment CH301 Vanden Bout LaBrake Fall 2013 left CH3Cl center CHCl3 right CCl4 Make a model of one of these molecules Use different colored clay balls for the different elements in compound Are there any polar bonds Are any of the molecules polar Are there a dipole moments CH301 Vanden Bout LaBrake Fall 2013 POLL CLICKER QUESTION 2 Polar or Nonpolar COCl2 CO32 Unit3Day3 LaBrake Page 4 CO32 COCl2 CH301 Vanden Bout LaBrake Fall 2013 Atomic Orbitals Molecular Shape How is it that we get from atomic orbitals with characteristic shapes to these bonds Overlapping orbitals H2 HF CH301 Vanden Bout LaBrake Fall 2013 Valence Bond Theory VB H H bond s s head on overlap yields sigma bond H F bond s p head on overlap yields sigma bond Unit3Day3 LaBrake Page 5 Think about methane CH4 2s22p2 overlapping with 1s 1 How is that possible CH301 Vanden Bout LaBrake Fall 2013 Make new atomic orbitals that are combinations of the old orbitals We call these hybrids one 2s three 2p s four sp3 CH301 Vanden Bout LaBrake Fall 2013 NEW HYBRIDIZED ORBITALS ARE DEGENERATE Unit3Day3 LaBrake Page 6 CH301 Vanden Bout LaBrake Fall 2013 EXPLAIN BONDING FOR AMMONIA CH301 Vanden Bout LaBrake Fall 2013 Use hybridization to explain the trigonal planar arrangement for example BF3 CH301 Vanden Bout LaBrake Fall 2013 Unit3Day3 LaBrake Page 7 When one s and two p oribitals are mixed to form a set of three sp2 orbitals one p orbital remains unchanged and is perpendicular to the plane of the hybrid orbitals CH301 Vanden Bout LaBrake Fall 2013 USE VB THEORY TO EXPLAIN BONDING IN ETHENE CH301 Vanden Bout LaBrake Fall 2013 Unit3Day3 LaBrake Page 8 VB multiple bond Ethene has a C C double bond LABEL THE SIGMA AND PI BONDS CH301 Vanden Bout LaBrake Fall 2013 USE VB THEORY TO PREDICT BONDING IN ETHYNE When one s orbital and one orbital are hybridized a set of two sp orbitals oriented at 180 degrees results two p orbitals left over for making pi bonds Unit3Day3 LaBrake Page 9 orbitals oriented at 180 degrees results two p orbitals left over for making pi bonds Examples of sp hybridization N2 HCCH CO2 CH301 Vanden Bout LaBrake Fall 2013 Hybridization of orbitals for CO2 CH301 Vanden Bout LaBrake Fall 2013 Unit3Day3 LaBrake Page 10 a An sp hybridized nitrogen atom b The s bond in the N2 molecule c the two p bonds in N2 are formed CH301 Vanden Bout LaBrake Fall 2013 Hybridization for expanded valence CH301 Vanden Bout LaBrake Fall 2013 Unit3Day3 LaBrake Page 11 State the hybridization and the number of sigma and pi bonds in the Structure CH301 Vanden Bout LaBrake Fall 2013 CH301 Vanden Bout LaBrake Fall 2013 Unit3Day3 LaBrake Page 12 WHAT HAVE WE LEARNED TODAY Using Molecular Shapes one can predict The polarity of the molecule The Molecular Shapes can be explained using the concept Valence Bond Theory Hybridized Orbitals CH301 Vanden Bout LaBrake Fall 2013 Learning Outcomes Apply the VB model to give the atomic hybridization of any atom in a given molecule Use the VB model to describe any bond in a molecule Determine if a molecule is polar based on polar bonds and its molecular geometry CH301 Vanden Bout LaBrake Fall 2013 Unit3Day3 LaBrake Page 13
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