Molecular Shape Covalent 4 No Grp Wk

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Molecular Shape Covalent 4 No Grp Wk

  1. 1. Molecular Shape Pp 259-262
  2. 2. VSEPR Theory <ul><li>Valence Shell Electron Pair Repulsion </li></ul><ul><li>Used to determine molecular shape </li></ul><ul><li>Based on arrangement that minimizes the repulsion between shared and unshared electrons </li></ul>
  3. 3. Bond Angle <ul><li>Angle formed by any two terminal atoms and a central atom </li></ul><ul><li>Caused by the repulsion of electron pairs </li></ul><ul><li>Supported by experimental evidence </li></ul><ul><li>Shared electron pairs repel each other </li></ul>
  4. 6. Lone pairs and VSEPR <ul><li>Lone pairs also important </li></ul><ul><li>Occupy a larger orbital than shared electrons </li></ul><ul><li>Lone pairs push shared orbitals together </li></ul>
  5. 8. VSEPR Definitions <ul><ul><li>Electron group –set of electrons that occupies a particular region around an atom. </li></ul></ul><ul><ul><li>Ligand – an atom or a group of atoms bonded to an inner atom </li></ul></ul><ul><ul><li>Steric number – the sum of the number of ligands plus the number of lone pairs; in other words, the total number of groups associated with that atom. </li></ul></ul>
  6. 11. <ul><li>Linear </li></ul><ul><li>180’ </li></ul><ul><li>Bent/angular </li></ul><ul><li><120’ </li></ul><ul><li>Bent/angular </li></ul><ul><li>104.5 </li></ul>
  7. 12. <ul><li>Trigonal planar </li></ul><ul><li>120’ </li></ul><ul><li>Tetrahedral </li></ul><ul><li>109.5’ </li></ul><ul><li>Trigonal pyramidal </li></ul><ul><li>107.3’ </li></ul>
  8. 13. <ul><li>Trigonal bipyramidal </li></ul><ul><li>90’ Horz to vert </li></ul><ul><li>120’ horz to horz </li></ul><ul><li>Octahedral </li></ul><ul><li>90’ </li></ul>
  9. 14. <ul><li>See-saw </li></ul><ul><li>Square planar </li></ul><ul><li>T-structure </li></ul><ul><li>Linear </li></ul><ul><li>Square pyramidal </li></ul>
  10. 16. Hybridization <ul><li>What’s a hybrid? </li></ul><ul><ul><li>Combining two of the same type of object and contains characteristics of both </li></ul></ul><ul><li>Occurs to orbitals during bonding </li></ul><ul><li>Hybridization </li></ul><ul><ul><li>Process in which atomic orbitals are mixed to form new hybrid orbitals </li></ul></ul><ul><ul><li>Each hybrid orbital contains one electron that it can share with another atom </li></ul></ul><ul><li>Carbon is most common atom to undergo hybridization </li></ul><ul><ul><li>Four hybrid orbitals from 1 s and 3 p orbitals </li></ul></ul><ul><ul><li>Hybrid= sp 3 orbital </li></ul></ul>
  11. 17. HYBRIDIZATION <ul><li>Mixture of two or more atomic orbitals of similar energies on the same atom to produce new hybrid atomic orbitals of equal energies </li></ul><ul><li>Orbitals of equal energy produced by the combination of two or more orbitals on the same atom </li></ul>Hybrid Orbital
  12. 20. <ul><li># of atomic orbitals mixed to form hybrid orbitals = the total # of pairs of shared electrons </li></ul><ul><li># of hybrid orbitals formed = # of atomic orbitals mixed </li></ul><ul><ul><li>1 s orbital + px + py + pz = 4 sp 3 hybrid orbitals </li></ul></ul><ul><li>CH 4 </li></ul><ul><li>AlCl 3 </li></ul><ul><li>Lone pairs also occupy hybrid orbitals </li></ul><ul><ul><li>H 2 O </li></ul></ul><ul><ul><li>BeCl 2 </li></ul></ul>
  13. 22. Class Work <ul><li>Lewis Dot Diagram (6 steps) </li></ul><ul><li>Molecular geometry </li></ul><ul><li>Bond Angle </li></ul><ul><li>Type of hybridization </li></ul><ul><li>New Lewis dot structure showing molecular shape </li></ul><ul><li>BF 3 </li></ul><ul><li>NH 4 + </li></ul><ul><li>OCl 2 </li></ul><ul><li>BeF 2 </li></ul><ul><li>CF 4 </li></ul><ul><li>AsH 3 </li></ul>

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