Remembering General Chemistry: Electronic Structure and Bonding Paula Yurkanis Bruice

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 sp3hybrid orbital on carbon also can bond with another sp3hybrid orbital from a neighboring carbon to form a carbon-carbon single bond Chapter 1

sp2Hybridization 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

sp2Hybridization 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

Remembering General Chemistry: Electronic Structure and Bonding Paula Yurkanis Bruice