Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Chemistry FIFTH EDITION by Steven S. Zumdahl University of Illinois

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 2 Chemistry FIFTH EDITION Chapter 9 Covalent Bonding: Orbitals Describe hybrid atomic orbitals.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 3 Bonding Chapter 8 –Write Lewis Structures. –Determine the Arrangement of e - pairs using VSEPR Theory. Chapter 9 –Determine the hybrid atomic orbitals used to form bonds.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 4 Hybridization The mixing of atomic orbitals to form special orbitals for bonding. The atoms are responding as needed to give the minimum energy for the molecule.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 5 Hybrid Orbitals Orbitals used to describe bonding that are obtained by taking combinations of atomic orbitals of the isolated atoms.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 6 Figure 9.1 (a) Lewis Structure (b) Tetrahedral Molecular Geometry of the Methane Molecule By experiment, CH 4 know to be tetrahedral with bond angles of . Experiments show 4 equivalent bonds.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 7 Figure 9.2 The Valence Orbitals on a Free Carbon Atom: 2s, 2p x, 2p y, and 2p z Bonding assumed to involve only the valence electrons. Overlap with these orbitals would not give  bond angles.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 8 Hybridization ☻☻☻ A new set of atomic orbitals might better serve the C atom in forming molecules. Hybridization = Modification of the localized electron model to account for the observation that atoms often seem to use special atomic orbitals in forming molecules.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 9 Figure 9.3 The Formation of sp 3 Hybrid Orbitals Let’s read together on p. 415 – “sp 3 hybridization.”

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 10 Figure 9.4 Cross Section of an sp 3 Orbital Each sp 3 orbital has 1)A large lobe pointing in one direction; 2) A small lobe Pointing in the other direction.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 11 Figure 9.5 An Energy-Level Diagram Showing the Formation of Four sp 3 Orbitals Four equivalent carbon orbitals.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 12 Figure 9.6 Tetrahedral Set of Four sp 3 Orbitals

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 13 Figure 9.7 The Nitrogen Atom in Ammonia is sp 3 Hybridized

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 14 Water, H 2 O H—O—H 4 pairs of e - requires sp 3 hybridization. O atom [He] ↑↓ ↑↓ ↑ ↑ 2s 2p O atom [He] ↑↓ ↑↓ ↑↓ ↑↓ hybrized sp 3 2 ↓’s from 2 H atoms

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 15 Ethylene H 2 C==CH 2 Each carbon atom is surrounded by three effective pairs. Requires a set of 3 orbitals with a trigonal planar geometry and 120  bond angles.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 16 Figure 9.8 The Hybridization of the s, p x, and p y Atomic Orbitals

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 17 Figure 9.9 An Orbital Energy-Level Diagram for sp 2 Hybridization One 2p orbital of carbon is not used. It remains a p orbital and perpendicular to the plane of the sp 2 hybrid orbitals.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 18 Figure 9.10 An sp 2 Hybridized C Atom

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 19 Two sp 2 orbitals on each carbon overlap with a 1s orbital from a H atom to share a pair of electrons. This results in the formation of 2 sigma bonds Between the one C atom and two H atoms.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 20 Figure 9.11 The  Bonds in Ethylene

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 21  (sigma) bond Formed by the sp 2 hybrid orbitals on each carbon – occupies space between the C atoms. Formed by the sp 2 hybrid orbitals on each carbon & the 1s orbital on hydrogen.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 22 Double Bond?? Results from sharing an additional pair of electrons in the space above & below the sigma bond. It uses the 2p orbital which  to the sp 2 orbitals. Results in a  (pi) bond.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 23 Figure 9.12 Sigma and Pi Bonding

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 24 Figure 9.13 The Orbitals for C 2 H 4

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 25 Whenever an atom is surrounded by 3 effective e - pairs, a set of sp 2 hybrid orbitals is required.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 26 A sigma (  ) bond centers along the internuclear axis. A pi (  ) bond occupies the space above and below the internuclear axis. Double Bonds

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 27 CO 2 O==C==O 2 effective pairs around central atom at an angle of 180 

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 28 Figure 9.14 When One s Orbital and One p Orbital are Hybridized, a Set of Two sp Orbitals Oriented at 180 Degrees Results

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 29 Figure 9.16 The Orbital Energy-Level Diagram for the Formation of sp Hybrid Orbitals on Carbon A set of two sp orbitals.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 30 Figure 9.17 The Orbitals of an sp Hybridized Carbon Atom Two sp hybridized orbitals. Two p unhybrized Orbitals.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 31 Figure 9.18 The Orbital Arrangement for an sp 2 Hybridized Oxygen Atom

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 32 Figure 9.15 The Hybrid Orbitals in the CO 2 Molecule

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 33 Figure 9.19 The Orbitals for CO 2

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 34 Figure 9.20 The Orbitals for N 2

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 35 PCl 5 5 e - pairs requires a geometry of trigonal bipyramidal. Requires dsp 3 hybridization.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 36 Figure 9.21 A Set of dsp 3 Hybrid Orbitals on a Phosphorus Atom

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 37 Each Cl is surrounded by 4 e - pairs. They require sp 3 hybridization.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 38 Figure 9.22 (a) The Structure of the PCl 5 Molecule (b) The Orbitals Used to Form the Bonds in PCl 5

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 39 SF 6 6 e - pairs requires a geometry of octahedral. Requires d 2 sp 3 hybridization.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 40 Figure 9.23 An Octahedral Set of d 2 sp 3 Orbitals on a Sulfur Atom

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 41 sp 3 hybrid orbitals on each F. sigma bond between d 2 sp 3 orbitals on S and sp 3 hybrid orbital on F Other three sp 3 orbitals on F hold lone pair e - ’s.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 42 The Localized Electron Model 4 Draw the Lewis structure(s) 4 Determine the arrangement of electron pairs (VSEPR model). 4 Specify the necessary hybrid orbitals.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 43 The Localized Electron Model: Summary Read this section. Summary in next slide – Figure 9.24

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 44 Figure 9.24 The Relationship of the Number of Effective Pairs, Their Spatial Arrangement, and the Hybrid Orbital Set Required See page 426.