Topic: Chemical Bonding Aim: What are chemical bonds & intermolecular forces? Do Now: Turn in your review sheet. Scan your notes & write down 5 facts you must know for tomorrow’s test. HW:

Chapter Objectives Explain energy changes & the relationship to stability Why bond? How does energy change? Explain how chemical bonds are formed Sharing Transferring Mobile e-

Chapter Objectives Metallic Mobile sea of e- holds atoms together Explain conductivity, malleability, luster, ductility

Chapter Objectives Ionic bonds Composition – metal & nonmetal Physical & chemical properties – hard, high mp/bp, conductivity as L or (aq) Show change in charge when drawing! Positive ion, lose e-, metals Negative ion, gain e-, nonmetals

Chapter Objectives Covalent Composition – nonmetals Physical/chemical properties (SPLash) Single – 2e-, one line Double – 4e-, 2 lines (O2, CO2) Triple – 6e-, 3 lines (N2) Nonpolar covalent (Br, I, N, Cl, H, O, F), equal sharing Polar covalent (different nonmetals), unequal sharing Larger difference in electronegativity, more polar Coordinate covalent (polyatomic ions) Molecular substances, network solids

Chapter Objectives Lewis dot structures Molecular Polarity To represent ionic – show charges To represent covalent – show overlap! Molecular Polarity Based on shape of molecule & distribution of charge SNAP – Symmetrical = Nonpolar, Asymmetrical = Polar

Chapter Objectives Intermolecular Forces Between molecules Weaker than bonds Dipole – between polar covalent mlcls Partial positive & partial negative charges of neighboring mlcls attract Hydrogen Bond – between mlcls containing H & either N, O, or F (Ex. NH3, H2O, HF) Same mechanism as dipole Strongest IM force

Chapter Objectives Van der Waals/Dispersion Forces Temporary, weak attraction btwn nonpolar mlcls e- move to 1 side of the molecule, giving it partially charged ends – they stick to one another Diatomics, noble gases Larger atom/molecule, stronger dispersion forces (stronger attraction) Why diatomics & noble gases can be liquified or frozen at low temperatures

Chapter Objectives Molecule-Ion Attraction Why polar substances can dissolve polar & ionic substances – they both have charges Water (polar) can dissolve other polar or ionic substances (salt, sugar) Nonpolar in nonpolar Like dissolves like

Chapter Objectives Vapor Pressure & Intermolecular Forces Table H Weak intermolecular forces – vaporize easily, low boiling point, high vapor pressure Strong intermolecular forces – difficult to vaporize, high boiling point, low vapor pressure