10.2-10.4 Sahara Williams

VSEPR Theory Electron groups repel one another through coulombic forces. The repulsion of between electron groups on interior atoms (central atoms) of a molecule determine the geometry of a molecule Used when looking at 2 dimensional Lewis structures to determine what they would look like in 3 dimensions

Determining Geometry Electron groups want to have maximum separation For molecules with one interior atom molecular geometry depends on The number of surrounding electron groups The number of bonding groups and lone pairs There are 5 basic shapes of molecules Linear geome6 Trigonal planar geometry Tetrahedral geometry Trigonal bipyramidal geometry Octahedral geometry

How to represent molecular geometry on paper

Linear Geometry Two electron groups 180 degrees of separation No lone pairs Y

Trigonal planar geometry Three electron groups 120 degree bond angles No lone pairs

Tetrahedral geometry Four electron groups 109.5 degree bond angles Contains unshared pairs

Trigonal Bipyramidal geometry Five electron groups Equatorial bond (the three bonds on the Trigonal plane) angles 120 degrees , axial bond (the two bonds on either side of the plane) angles 90 degrees Contains unshared pairs

Octahedral geometry Six electron groups Bond angles 90 degrees Contains unshared pairs

Lone pairs Electron geometry- the geometrical arrangement of electron groups Molecular geometry- the geometrical arrangement of atoms Lone pairs exert slightly greater repulsion than bonding electrons

Four electron groups with lone pairs Electron geometry is tetrahedral Molecular geometry is Trigonal pyramidal Bond angles for 1 unshared pair is 107 degrees Bond angles for 2 unshared pairs is 104.5 degrees

Five electron groups with lone pairs Electron geometry is Trigonal Bipyramidal 1 group of unshared electrons occupy the equatorial position Two 90 degree interactions - seesaw 2 groups of unshared electrons occupy the Equatorial position Two 90 degree interaction - t shaped 3 groups of unshared pairs occupy 3 Equatorial positions Linear geometry

Six electron groups with lone pairs Electron geometry is octahedral 1 unshared pair is square pyramidal 2 unshared pairs are square planar

Predicting geometries for larger molecules Larger molecules have 2 or more interior atoms Draw the Lewis structure of the given molecule determine the geometry of each interior atom Connect them from left to right.