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Chapter 10 Bonding and Molecular Structure: Orbital Hybridization and Molecular Orbitals Dr. S. M. Condren

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**Advanced Theories of Chemical Bonding**

Atomic Orbitals Molecules Dr. S. M. Condren

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**Two Theories of Bonding**

MOLECULAR ORBITAL THEORY — Robert Mullikan ( ) valence electrons are delocalized valence electrons are in orbitals (called molecular orbitals) spread over entire molecule. Dr. S. M. Condren

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**Two Theories of Bonding**

VALENCE BOND THEORY — Linus Pauling valence electrons are localized between atoms (or are lone pairs). half-filled atomic orbitals overlap to form bonds. Dr. S. M. Condren

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**Sigma Bond Formation by Orbital Overlap**

Two s orbitals overlap Dr. S. M. Condren

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**Sigma Bond Formation Two s orbitals overlap One s and one p orbital**

Two p orbitals overlap Dr. S. M. Condren

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**Using VB Theory Bonding in BF3 planar triangle angle = 120o**

Dr. S. M. Condren

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Bonding in BF3 How to account for 3 bonds 120o apart using a spherical s orbital and p orbitals that are 90o apart? Pauling said to modify VB approach with ORBITAL HYBRIDIZATION — mix available orbitals to form a new set of orbitals — HYBRID ORBITALS — that will give the maximum overlap, in the correct geometry. Dr. S. M. Condren

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**Bonding in BF3 rearrange electrons hydridize orbs. unused p orbital**

three sp2 hybrid orbitals 2p 2s Dr. S. M. Condren

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Bonding in BF3 The three hybrid orbitals are made from 1 s orbital and 2 p orbitals 3 sp2 hybrids. Now we have 3, half-filled HYBRID orbitals that can be used to form B-F sigma bonds. Dr. S. M. Condren

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Bonding in BF3 An orbital from each F overlaps one of the sp2 hybrids to form a B-F bond. Dr. S. M. Condren

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BF3, Planar Trigonal Dr. S. M. Condren

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**Bonding in CH4 How do we account for 4 C—H sigma bonds 109o apart?**

Need to use 4 atomic orbitals — s, px, py, and pz — to form 4 new hybrid orbitals pointing in the correct direction. Dr. S. M. Condren

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Bonding in CH4 Dr. S. M. Condren

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**Bonding in a Tetrahedron — Formation of Hybrid Atomic Orbitals**

4 C atomic orbitals hybridize to form four equivalent sp3 hybrid atomic orbitals. Dr. S. M. Condren

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Dr. S. M. Condren

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Bonding in Glycine Dr. S. M. Condren

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**Orbital Hybridization**

BONDS SHAPE HYBRID REMAIN 2 linear sp 2 p’s 3 trigonal sp2 1 p planar 4 tetrahedral sp3 none Dr. S. M. Condren

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Multiple Bonds Consider ethylene, C2H4 Dr. S. M. Condren

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Sigma Bonds in C2H4 Dr. S. M. Condren

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π Bonding in C2H4 The unused p orbital on each C atom contains an electron and this p orbital overlaps the p orbital on the neighboring atom to form the π bond. Dr. S. M. Condren

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π Bonding in C2H4 The unused p orbital on each C atom contains an electron and this p orbital overlaps the p orbital on the neighboring atom to form the π bond. Dr. S. M. Condren

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Multiple Bonding in C2H4 Dr. S. M. Condren

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s and π Bonding in C2H4 Dr. S. M. Condren

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s and π Bonding in CH2O Dr. S. M. Condren

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s and π Bonding in C2H2 Dr. S. M. Condren

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s and π Bonding in C2H2 Dr. S. M. Condren

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**Consequences of Multiple Bonding**

There is restricted rotation around C=C bond. Dr. S. M. Condren

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**Consequences of Multiple Bonding**

Restricted rotation around C=C bond. Dr. S. M. Condren

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**Diatomic Molecules AO MO AO H H2 H 1s 1s ENERGY B - AB 2 - 0**

B => bonding electrons B - AB B.O. = = = 1 AB => antibonding electrons all electrons are paired, thus diamagnetic Dr. S. M. Condren

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**Diatomic Molecules AO MO AO He He2 He 1s 1s ENERGY B - AB 2 - 2**

Zero bond order means it does not exist B - AB B.O. = = = 0 Dr. S. M. Condren

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**Diatomic Molecules AO MO AO He He2 He+ 1s 1s ENERGY B - AB 2 - 1**

B.O. = = = 1/2 One unpaired electron, thus, paramagnetic Dr. S. M. Condren

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AO B MO B2 AO B 2p 2p 2s 2s 1s nonbonding 1s Dr. S. M. Condren

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**Molecular Orbital Diagram**

antibonding MO end-to-end bonding MO antibonding MO side-by-side bonding MO Dr. S. M. Condren

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AO C MO C2 AO C 2p 2p 2s 2s 1s nonbonding 1s Dr. S. M. Condren

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AO O MO O2 AO O 2p 2p 2s 2s 1s nonbonding 1s Dr. S. M. Condren

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Energy Dr. S. M. Condren

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