I. Introduction to Bonding

Common Molecular Shapes4 total2 bond2 loneBENT104.5H2O

Chemical Bondattractive force between atoms or ions that binds them together as a unitbonds form in order todecrease potential energy (PE)increase stabilityCOMPOUNDTernaryCompoundBinaryCompound2 elementsmore than 2elementsNaNO3NaClIonic Bonding - Crystal Lattice

Ionic Bonds

Covalent Bonding - True Molecules

Diatomic MoleculeMetallic Bonding - Electron Sea

Bond PolarityMost bonds are a blend of ionic and covalent characteristics.Difference in electronegativity determines bond type.

Bond PolarityElectronegativityAttraction an atom has for a shared pair of electrons.higher e-neg atom -lower e-neg atom +Bond PolarityElectronegativity Trend (p. 151)Increases up and to the right.

Bond PolarityNonpolar Covalent Bonde- are shared equallysymmetrical e- densityusually identical atoms

+-Polar Covalent Bonde- are shared unequallyasymmetrical e- densityresults in partial charges (dipole) Nonpolar

Polar

Ionic

Bond PolarityExamples:Cl2HClNaCl

3.0-3.0=0.0Nonpolar3.0-2.1=0.9Polar3.0-0.9=2.1IonicChemical Bondattractive force between atoms or ions that binds them together as a unitbonds form in order todecrease potential energy (PE)increase stability

Lewis Diagrams

Molecular StructureIRuleRememberMost atoms form bonds in order to have 8 valence electrons.

Hydrogen 2 valence e-

Groups 1,2,3 get 2,4,6 valence e-Expanded octet more than 8 valence e- (e.g. S, P, Xe)Radicals odd # of valence e-A. Octet RuleExceptions:F B FFH O HN OVery unstable!!F FF S FF FB. Drawing Lewis DiagramsFind total # of valence e-.Arrange atoms - singular atom is usually in the middle.Form bonds between atoms (2 e-).Distribute remaining e- to give each atom an octet (recall exceptions).If there arent enough e- to go around, form double or triple bonds.B. Drawing Lewis DiagramsCF41 C 4e- = 4e-4 F 7e- = 28e- 32e-FF C FF - 8e- 24e-B. Drawing Lewis DiagramsBeCl21 Be 2e- = 2e-2 Cl 7e- = 14e- 16e-Cl Be Cl - 4e- 12e-B. Drawing Lewis DiagramsCO21 C 4e- = 4e-2 O 6e- = 12e- 16e-O C O - 4e- 12e-C. Polyatomic IonsTo find total # of valence e-:Add 1e- for each negative charge.Subtract 1e- for each positive charge.Place brackets around the ion and label the charge.C. Polyatomic IonsClO4-1 Cl 7e- = 7e-4 O 6e- = 24e- 31e-OO Cl OO + 1e- 32e- - 8e- 24e-C. Polyatomic IonsNH4+1 N 5e- = 5e-4 H 1e- = 4e- 9e-HH N HH - 1e- 8e- - 8e- 0e-C. Polyatomic IonsOH-1 O 6e- = 6e-1 H 1e- = 1e- 7e- O H

+ 1e- 8e- - 8e- 0e-D. Resonance StructuresMolecules that cant be correctly represented by a single Lewis diagram.Actual structure is an average of all the possibilities.Show possible structures separated by a double-headed arrow.

D. Resonance StructuresOO S OOO S OOO S OSO3

Molecular Geometry

IVSEPR TheoryValence Shell Electron Pair Repulsion TheoryElectron pairs orient themselves in order to minimize repulsive forces.

VSEPR TheoryTypes of e- PairsBonding pairs - form bondsLone pairs - nonbonding e-Lone pairs repel more strongly than bonding pairs!!!VSEPR TheoryLone pairs reduce the bond angle between atoms.

Bond AngleDetermining Molecular ShapeDraw the Lewis Diagram.Tally up e- pairs on central atom.double/triple bonds = ONE pairShape is determined by the # of bonding pairs and lone pairs.Know the 8 common shapes & their bond angles!Common Molecular Shapes2 total2 bond0 lone

LINEAR180BeH2Common Molecular Shapes3 total3 bond0 loneTRIGONAL PLANAR120

BF3Common Molecular Shapes3 total2 bond1 loneBENT