Chapter 8 MOLECULAR STRUCTURE COVALENT BONDING THEORIES Two

Chapter 8 MOLECULAR STRUCTURE & COVALENT BONDING THEORIES

Two Simple Theories of Covalent Bonding � Valence Shell Electron Pair Repulsion Theory �_____ �R. J. Gillespie - 1950’s � Valence Bond Theory �__________ �L. Pauling - 1930’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 = 109. 5 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 = 104. 50

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 _____109. 50

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

Name of orbital – number of pairs on central atom (Regions of high e- density around the central atom) sp - 2 sp 2 - 3 sp 3 - 4 sp 3 d - 5 sp 3 d 2 - 6 Shape (name) of orbital

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. _____ _, Be. Br 2, Be. I 2, Hg. Cl 2, Cd. Cl 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

AB 4 Molecules - No Lone Pairs on A - Tetrahedral Molecules � Ex. _____ ___, CF 4, CCl 4, Si. H 4, Si. F 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

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, __________

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

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, __________

AB 5 - No Lone Pairs Trigonal Bipyramidal Molecules � Ex. PF 5, As. F 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. molecules have a _____shaped molecular geometry and are _____ ___. � AB 4 U 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 molecules have a _____ molecular geometry and are _____ � AB 3 U 2 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 molecules have a _____ ___molecular geometry and are _____ � AB 2 U 3 Xe. F 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. molecules have a _________ molecular geometry and are _____ __. � AB 5 U 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. molecules have a _____ molecular geometry and are _____ __. � AB 4 U 2 Xe. F 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?