What determines molecular shape? Bond angles: angle formed between two adjacent bonds on the same atom e.g. CCl 4 Chapter 9: Molecular Geometry and Bonding Theories bond angle: ?

Lewis Structures What determines molecular shapes? => tell us how atoms are physically connected No information regarding the actual 3-D structure of molecules Chapter 9: Molecular Geometry and Bonding Theories

Repulsion of valence electrons => largest possible separation of atoms V alence- S hell E lectron- P air R epulsion Model Chapter 9: Molecular Geometry and Bonding Theories

Different ways of depicting 3-D structure bonds in plane of paper bond in front of the paper plane bond behind of the paper plane "Ball and Stick""Spacefilling" Chapter 9: Molecular Geometry and Bonding Theories

nonbonding pair bonding pair Types of Electron Domains: ● nonbonding (or "lone") electrons ● single OR double OR triple bonding electrons Lewis structures show number of electron domains Chapter 9: Molecular Geometry and Bonding Theories => Bonding AND non-bonding electron pairs take up space

Molecular shape depends on electron domain geometry Lewis Structures tell us … ● where bonds (bonding electron pairs) are ● the location of nonbonding electrons Bonding AND non-bonding electron pairs take up space Chapter 9: Molecular Geometry and Bonding Theories } around the central atom

Possible Electron Domain Geometries: Linear Trigonal Planar Tetrahedral Trigonal Bipyramidal Octahedral Chapter 9: Molecular Geometry and Bonding Theories 180 o 120 o o 120 o 90 o

4 electron domains around central atom => electron domain geometry: Tetrahedral nonbonding pair bonding pair Lewis structures → electron domain geometry → molecular geometry Chapter 9: Molecular Geometry and Bonding Theories 3 non-bonding + 1 bonding electron domain

Lewis structures → electron domain geometry → molecular geometry Chapter 9: Molecular Geometry and Bonding Theories 4 electron domains around central atom => electron domain geometry: Tetrahedral

Lewis structures → electron domain geometry → molecular geometry Chapter 9: Molecular Geometry and Bonding Theories 3 electron domains around central atom => electron domain geometry: Trigonal planar

Lewis structures → electron domain geometry → molecular geometry Chapter 9: Molecular Geometry and Bonding Theories 4 electron domains around central atom => electron domain geometry: Tetrahedral +

Lewis structures → electron domain geometry → molecular geometry Chapter 9: Molecular Geometry and Bonding Theories 2 electron domains around central atom => electron domain geometry: Linear

Lewis structures → electron domain geometry → molecular geometry Chapter 9: Molecular Geometry and Bonding Theories 3 electron domains around central atom => electron domain geometry: Trigonal planar

4 electron domains: => electron domain geometry Tetrahedral 3 bonds, 1 nonbonding pair: => molecular geometry Trigonal pyramidal Chapter 9: Molecular Geometry and Bonding Theories Lewis structures → electron domain geometry → molecular geometry Molecular Geometry depends on how many of the electron domains are actually bonds

Bond angles can be distorted: o 107 o o ● nonbonding electron pairs occupy more volume than bonding pairs Chapter 9: Molecular Geometry and Bonding Theories

Bond angles can be distorted ● multiple bonds occupy a larger volume than single bonds o o lone pairs => triple bonds => double bonds => single bonds Volume Chapter 9: Molecular Geometry and Bonding Theories

Elements from the 3rd period onward.. ● have d -orbitals ● can have an expanded valence shell ● may have more than 4 electron domains surrounding them e.g. phosphorous: P: [Ne] 3s 2 3p 3 3s3p 3d "expanded" valence shell Chapter 9: Molecular Geometry and Bonding Theories

Equatorial bond Axial bond

Chapter 9: Molecular Geometry and Bonding Theories

TeF 6 # electron domains electron domain geometry molecular geometry Chapter 9: Molecular Geometry and Bonding Theories

H3O+H3O+ + # electron domains electron domain geometry molecular geometry Chapter 9: Molecular Geometry and Bonding Theories

NO 2 # electron domains electron domain geometry molecular geometry Chapter 9: Molecular Geometry and Bonding Theories

SO 3 # electron domains electron domain geometry molecular geometry Chapter 9: Molecular Geometry and Bonding Theories

SCl 2 # electron domains electron domain geometry molecular geometry Chapter 9: Molecular Geometry and Bonding Theories

SbI 5 # electron domains electron domain geometry molecular geometry Chapter 9: Molecular Geometry and Bonding Theories

The VESPR model can be extended to larger molecules e.g. glycine : Electron-domain geometry: predicted bond angles: ? ? ? ? Chapter 9: Molecular Geometry and Bonding Theories