6/20/2015 One Point Quiz  One quiz per table, list everyone’s name  Agree on an answer  You have two minutes

6/20/2015 Unknown Dues Dates  Unknown AFriday, Week 5  Unknown BFriday, Week 7  Unknown CFriday, Week 9  Unknown DFriday, Week 10

VSEPR Valence Shell Electron Pair Repulsion Edward A. Mottel Department of Chemistry Rose-Hulman Institute of Technology

6/20/2015 Bonding Theories  Ionic Model  Skeleton Diagrams  Lewis Dot Diagrams  Molecular Orbital Theory  Orbital Hybridization  Valence Bond Theory  Valence Shell Electron Pair Repulsion

6/20/2015 VSEPR Valence Shell Electron Pair Repulsion  Allows the prediction of molecular geometry An extension of the “groups of electrons” (effective electron pair) concept Involves sp and dsp types of hybridizations The central atom may or may not obey the octet rule.

6/20/2015 To Determine Molecular Geometry  Count the number of valence electrons.  Place a pair of electrons between the atoms bound together.  Each non-central (terminal) atom is given electrons to fulfill its inert gas configuration.  Any additional electron pairs become lone (unshared) electrons pairs on the central atom.  The geometry is determined by the number of bonding and unshared pairs of electrons on the central atom.

6/20/2015 Consider the Possible Combinations Atoms Bound to the Central Atom Number of Lone Electron Pairs What is the preferred geometry for the blocks shown in blue?

6/20/2015 Zero Lone Pairs of Electrons Around the Central Atom Number of Atoms Bound to the Central Atom ArrangementGeometryExample 1 A B linearH2H2 2 A BB BeH 2 3 B A BB trigonal planar BF 3

6/20/2015 Zero Lone Pairs of Electrons Around the Central Atom Number of Atoms Bound to the Central Atom ArrangementGeometryExample 4 A B B B B tetrahedralCH 4 5 A B B B B B trigonal bipyramidal PCl 5

6/20/2015 Zero Lone Pairs of Electrons Around the Central Atom Number of Atoms Bound to the Central Atom ArrangementGeometryExample 6 A B B B B B B octahedralSF 6

6/20/2015 AB Type Molecules with Unshared Pairs of Electrons 1 A B linearCO A B 2linearO2O2 3 A B HF ArrangementGeometryExample Number of Lone Electron Pairs on Central Atom

Molecular Models Look at the various molecular models The blue sphere represents an atom The “paddle” represents a pair of electrons Only atoms can be “seen”. What is the shape of each molecule?

6/20/2015 AB 2 Type Molecules with Unshared Pairs of Electrons 1 A BB  bent  120º) O3O3 2 A BB H2OH2O  bent  109º) 3 A B B linearXeF 2 ArrangementGeometryExample Number of Lone Electron Pairs on Central Atom

6/20/2015 AB 3 Type Molecules with Unshared Pairs of Electrons 1 A B B B trigonal pyramidal NH 3 A B B B 2T-shapedClF 3 ArrangementGeometryExample Number of Lone Electron Pairs on Central Atom

6/20/2015 AB 4 Type Molecules with Unshared Pairs of Electrons A B B B B 1 sawhorse, see-saw TeCl 4 A B B B B 2 square planar XeF 4 ArrangementGeometryExample Number of Lone Electron Pairs on Central Atom

6/20/2015 AB 5 Type Molecules with Unshared Pairs of Electrons A B B B B B square pyramidal 1IF 5 ArrangementGeometryExample Number of Lone Electron Pairs on Central Atom

6/20/2015 Lone Electron Pair Position  The lone pairs always occur in the equatorial plane. Maximizes the angular separation between lone pairs and other electron pairs.

6/20/2015 Summary of Observed Geometries 1 linear 2 bent (  120º) bent (  109º) linear 3 trigonal planar trigonal pyramidal T-shaped 4 tetrahedral sawhorse, see-saw square planar 5 trigonal bipyramidal square pyramidal 6 octahedral Atoms Bound to the Central Atom Number of Lone Electron Pairs

6/20/2015

Skeleton Diagrams of Molecules N H HH O HH A BB A B B B B A B B B B B A BB A B A B A B ºº B A BB A BB A B B A B B B A B B B B A B B B

6/20/2015 Skeleton Diagrams of Molecules A B BB B N H HH B A BB A BB A B A B B B B A B B B B B A B B B B B B A B B B B B A B B B B