Chapter 8

Two Simple Theories of Covalent Bonding  Valence Shell Electron Pair Repulsion Theory __________ R. J. Gillespie ’s  Valence Bond Theory __________ __________ L. Pauling ’s & 40’s

VSEPR Theory  regions of __________ electron density around the central atom are as far apart as possible to __________ repulsions  __________ basic shapes based on # of regions of high electron density  several __________ ____of these five basic shapes will also be examined

VSEPR Theory 1 st shape: _____regions of high electron density

VSEPR Theory 2 nd shape: _____ regions of high electron density

VSEPR Theory 3 rd shape: _____ regions of high electron density

VSEPR Theory 4 th shape: _____ regions of high electron density

VSEPR Theory 5 th shape: _____ regions of high electron density

VSEPR Theory  _____ ________ _______– the arrangement of the valence shell electrons around the central atom determined by the locations of regions of high electron density around the central atom(s) (includes both elements and lone pairs of electrons)  _____ __________ _____- determined by the arrangement of atoms around the central atom(s) What the molecule really looks like (only elements) _____ __________ __________ __________ __________ __________ __________ __________

VSEPR Theory  CH 4 vs. H 2 O  CH 4 - methane  electronic geometry _____  molecular geometry _____ bond angles = o

VSEPR Theory  _____ _____of electrons (unshared pairs) require more volume than shared pairs  there is an ordering of _____ _____of electrons around central atom  H 2 O - water  electronic geometry _____  molecular geometry _____ __________ _____ bond angle =

VSEPR Theory 1. lone pair to lone pair repulsion is _____ _____ 2. lone pair to bonding pair repulsion is _____ _____ 3. bonding pair to bonding pair repulsion is _____ ___  lone pair to lone pair repulsion is why bond angles in water are _____ _____

Valence Bond Theory  covalent bonds are formed by _____ _____of atomic orbitals  atomic orbitals on the _____ _____atom can mix and exchange their character – _____ __________ _____  _____ __________ _____ pink flowers, mules, corn, grass

Hybrid orbitals From orbital diagrams Hybridization - CP s + p orbitals  s + p + p orbitals  s + p + p + p orbitals  s + p + p + p + d orbitals  s + p + p + p + d + d orbitals  helps describe the same shapes as VSEPR – (hybridization – mixing of orbitals)

Name of orbital – number of pairs on central atom (Regions of high e - density around the central atom) Shape (name) of orbital sp - 2 sp sp sp 3 d-5 sp 3 d 2 - 6

Molecular Geometry Terminology  In the next sections the following terminology will be used A = central atom B = bonding pairs around central atom U = lone pairs around central atom For example: AB 3 U designates that there are _____ _____ pairs and _____ __________ _____ around the central atom (_____ __________ ____)

AB 2 Molecules - No Lone Pairs on A - Linear Molecules  Ex. _____ _, BeBr 2, BeI 2, HgCl 2, CdCl 2 ~ all are _____ ___, _____ ___molecules  Dot Formula Electronic Geometry

AB 2 Molecules - No Lone Pairs on A - Linear Molecules  VSEPR Polarity

AB 2 Molecules - No Lone Pairs on A - Linear Molecules Molecular Geometry same as electronic geometry__________ Molecular Geometry

AB 3 Molecules - No Lone Pairs on A - Trigonal Planar Molecules  Examples: BF 3, _____ __  all are _____ __________ _____, _____ ____ molecules  Dot Formula Electronic Geometry

AB 3 Molecules - No Lone Pairs on A - Trigonal Planar Molecules  VSEPR Polarity

AB 3 Molecules - No Lone Pairs on A - Trigonal Planar Molecules Molecular Geometry same as electronic geometry, symmetrical & nonpolar Molecular Geometry

AB 4 Molecules - No Lone Pairs on A - Tetrahedral Molecules  Ex. _____ ___, CF 4, CCl 4, SiH 4, SiF 4  all are _____ _____, _____ ___molecules ~ as long as they have the same 4 _____ _____  Dot Formula Electronic Geometry

AB 4 Molecules - No Lone Pairs on A - Tetrahedral Molecules  VSEPR Polarity

AB 4 Molecules - No Lone Pairs on A - Tetrahedral Molecules Molecular Geometry same as electronic geometry, symmetrical & nonpolar Molecular Geometry

AB 3 U Molecules - One Lone Pair - Pyramidal Molecules  examples NH 3, NF 3  first example of _____ _____on the central atom electronic and molecular geometry are different all 3 substituents can be the same but molecule is _____ _____  NH 3 and NF 3 are _____ _____, _____ molecules

AB 3 U Molecules - One Lone Pair - Pyramidal Molecules  Dot Formulas Electronic Geometry Molecular Geometry - different from the electronic geometry, _____ __________ __________ _____ Molecular Geometry

AB 3 U Molecules - One Lone Pair - Pyramidal Molecules  VSEPR Polarity

AB 3 U Molecules - One Lone Pair - Pyramidal Molecules  VSEPR Polarity

AB 2 U 2 - Two Lone Pairs - V-Shaped Molecules  Example H 2 O  water is an angular, _____ __________ __, _____ _____molecule Dot Formula Electronic Geometry Molecular Geometry - different from electronic geometry, asymmetrical & polar Molecular Geometry

AB 2 U 2 - Two Lone Pairs - V-Shaped Molecules  VSEPR Polarity

ABU 3 - Three Lone Pairs - Linear Molecules  Hydrogen halides - ___, HCl, HBr, HI  Dot Formula Electronic Geometry

ABU 3 - Three Lone Pairs - Linear Molecules  VSEPR Polarity HF is a polar molecule. Molecular Geometry - different from electronic geometry, _____ __________ __________ _____ Molecular Geometry

AB 5 - No Lone Pairs - Trigonal Bipyramidal Molecules  Ex. PF 5, AsF 5, PCl 5, etc. All are _____ __________ _____, _____ _____ molecules.  Dot Formula Electronic Geometry

AB 5 - No Lone Pairs - Trigonal Bipyramidal Molecules  VSEPR Polarity

AB 5 - No Lone Pairs - Trigonal Bipyramidal Molecules  Polarity Molecular Geometry

AB 5 - No Lone Pairs - Trigonal Bipyramidal Molecules  Valence Bond (Hybridization)

AB 4 U- One Lone Pair - Seesaw Molecules  For one lone pair an AB 4 U molecule results.  AB 4 U molecules have a _____ ____ shaped molecular geometry and are _____ ___. SF 4 is an AB 4 U molecule _____ _____ occupies an _____ _____ position

AB 4 U- One Lone Pair - Seesaw Molecules  VSEPR Molecular Geometry

AB 3 U 2 - Two Lone Pairs - T-shaped Molecules  For two lone pairs an AB 3 U 2 molecule results  AB 3 U 2 molecules have a _____ _____ molecular geometry and are _____ _____ IF 3 is an AB 3 U 2 molecule _____ __________ _ occupy _____ _____ positions

AB 3 U 2 - Two Lone Pairs - T-shaped Molecules  VSEPR Molecular Geometry

AB 2 U 3 - Three Lone Pairs - Linear Molecules  For three lone pairs an AB 2 U 3 molecule results  AB 2 U 3 molecules have a _____ ___ molecular geometry and are _____ _____ XeF 2 is an AB 2 U 3 molecule _____ __________ __ occupy _______ __ positions

AB 2 U 3 - Three Lone Pairs - Linear Molecules  VSEPR Molecular Geometry

AB 6 - No Lone Pairs - Octahedral Molecules  Ex. SF 6, _____ __, SCl 6, etc.  These are _____ _____and _____ ___ molecules if all 6 substituents are the _____ ___  Dot Formula Electronic Geometry Molecular Geometry

AB 6 - No Lone Pairs - Octahedral Molecules  VSEPR Polarity

AB 6 - No Lone Pairs - Octahedral Molecules  Valence Bond (Hybridization)

AB 5 U- One Lone Pair - Square Pyramidal Molecules  For one lone pair an AB 5 U molecule results.  AB 5 U molecules have a _____ _________ molecular geometry and are _____ __. IF 5 is an AB 5 U molecule _____ _____ occupies an _____ __ position

AB 5 U- One Lone Pair - Square Pyramidal Molecules  VSEPR Molecular Geometry

AB 4 U 2 - Two Lone Pairs - Square Planar Molecules  For two lone pairs an AB 4 U 2 molecule results.  AB 4 U 2 molecules have a ________ _____ molecular geometry and are _____ __. XeF 4 is an AB 4 U 2 molecule _____ lone pairs occupy _____ __ positions

AB 5 U- One Lone Pair - Square Pyramidal Molecules  VSEPR Molecular Geometry

Summary of Electronic & Molecular Geometries

 The structure of penicillin-G is shown below. What is the electron geometry, molecular geometry, and hybridization of each of the 10 indicated atoms in penicillin-G?