University of California, Chapter 1 Remembering General Chemistry: Electronic Structure and Bonding Paula Yurkanis Bruice University of California, Santa Barbara

Contents of Chapter 1 Bonding, Lewis Structures Atomic & Molecular Orbitals Hybrid Orbitals Single Bonds Multiple Bonds Chapter 1

Ionic Bonds Chapter 1

Covalent Bonds covalent bond Chapter 1

Polar Covalent Bonds Chapter 1

Bond Polarity Depends on Electronegativity Differences

Polar Covalent Bonds There is a continuum of bonding types Chapter 1

Lewis Structures The chemical symbols we have been using in which valence electrons are shown as dots are called Lewis structures Chapter 1

Drawing Lewis Structures Write the symbols for the elements in the correct structural order Consider nitric acid, HNO3 Chapter 1

Sticks and Eyeballs Bonds + Lone Pairs = 4 (Octet Rule) Exceptions: H has 1 bond, B has 3 bonds Bonds: Count spaces from noble gas Convert bond to LP is (-), LP to bond is (+) Exceptions: C(+), B(-) Chapter 1

Formal Charges Subtract the number of assigned electrons from the number of valence electrons (core charge) for an uncombined atom of the same element 6 - 6 = 0 1 - 1 = 0 6 - 7 = -1 6 - 6 = 0 5 - 4 = +1 Chapter 1

Condensed Structural Formulas Kekulé formulas also are called structural formulas Often, structural formulas are condensed becomes Chapter 1

1s and 2s Orbitals Chapter 1

2p Orbitals Chapter 1

Molecular Orbital From p Electrons Molecular orbitals also can be formed from p orbitals Chapter 1

Hybrid Orbitals Methane, CH4, has four equivalent carbon-hydrogen bonds Chapter 1

Hybridization Theory: Mix the 2s orbital with the three 2p orbitals to form four equivalent hybrid orbitals Chapter 1

Hybridization - Tetrahedral Carbon The sp3 hybrid orbital on carbon also can bond with another sp3 hybrid orbital from a neighboring carbon to form a carbon-carbon single bond Chapter 1

sp2 Hybridization in Ethene The carbon-carbon bond formed from the overlap of an sp2 orbital on one carbon with an sp2 orbital on a neighboring carbon atom results in an orbital which is cylindrically symmetric about the carbon-carbon axis Chapter 1

sp2 Hybridization in Ethene A second bond is formed between the two carbon atoms via the side-by-side overlap of the remaining (un-hybridized) p orbitals Electron density accumulates above and below the carbon-carbon axis Chapter 1

sp Hybridization in Ethyne The overlap of the sp hybrid orbitals forms a  bond Chapter 1

sp Hybridization in Ethyne The remaining p orbitals overlap side-by-side, forming  bonds with electron density above and below the carbon-carbon axis as well as in front and in back Chapter 1

Summary of Orbital Hybridization Count the number of objects attached to an atom. Each LP is an object, each neighboring atom is an object. Each object needs one orbital to build hybrids Start with an s orbital, then use up to 3 p orbitals as needed Only LP’s remain in hybrids when bonds form Chapter 1

Summary of Orbital Hybridization Chapter 1