C121 11-3 lec22GL

C121 11-3 lec22GL - Lecture 22 October 31, 2011 Bonding:...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Lecture 22 October 31, 2011 Bonding: Specific Models Last Day: Covalent Bonding (contd) Bond Energies and Chemical Reactions (13.8) Electronegativity (13.2) Bond Polarity and Dipole Moments (13.3) Polar Covalent Bonds Today: Models of Bonding I Localized Electron Bonding Models (i) Lewis Structures Rules, Formal Charge, and Exceptions (ii) Valence Shell Electron Pair Repulsion Theory (ii) Hybrid Atomic Orbital Theory II Molecular Orbital Theory Bond Energies and Chemical Reactions uH rxn = Reactants ProdUcts Energy absorbed to break reactant bonds + Energy released in forming prodUct bonds uH rxn = D(bonds broken) D(bonds formed) Electronegativity and Bond Polarity electronegativity values ( ) allow us to gain insight into the degree of polar (ionic) character that exists in a covalent bond. For the diatomic molecule A-B ionic large polar covalent moderate covalent zero Type of Bond U(electronegativity) A - B bonding continuum % Ionic Character of Gas Phase Diatomic Molecules H-X 565 1.83 42% | 2.2 4.0 | = 1.8 H-F 427 1.11 17% | 2.2 3.0 | = 0.8 H-Cl 363 0.78 15% | 2.2 - 2.8 | = 0.6 H-Br Bond Energy kJ/mol Dipole Moment (Debye) % Ionic Character | H- X | Diatomic Molecule increase in bond polarity is reflected in the increase in bond strength Ionic Character versus Electronegativity Difference Bonding Models for Covalent Molecules Bonding models are: oversimplifications not necessarily reflecting reality useful tools allowing us to understand, systematize and predict molecular structure (and reactivity) based on assumptions that limit our interpretations individual bonds makes it much easier to deal with complex molecules such as DNA.complex molecules such as DNA....
View Full Document

Page1 / 24

C121 11-3 lec22GL - Lecture 22 October 31, 2011 Bonding:...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online