1. More bonding Quick Overview of: Ionic Bonding Metallic bonding Hydrogen bonding Quick Overview of: Ionic Bonding Metallic bonding Hydrogen bonding

2. OBJECTIVES - BONDING LEARN ABOUT STABLE ELECTRON CONFIGURATIONS UNDERSTAND FACTORS GOVERNING IONIC SIZE UNDERSTAND ELECTRON SEA MODEL EXPLAIN DIPOLE-DIPOLE ATTRACTION AND HYDROGEN BONDING REVIEW LONDON DISPERSION FORCES

3. STABLE ELECTRON CONFIGURATIONS IN STABLE COMPOUNDS, ATOMS TEND TO ACHIEVE THE ELECTRON CONFIGURATION OF THE NEAREST NOBLE GAS

4. ionic compounds Non-Metals gain e- obtain configuration of next noble gas Metals lose e- obtain configuration of previous noble gas

5. Ionic Compounds Ions group together to form electrically neutral compounds

6. Ionic size When a metal loses e -, cation is smaller than neutral atom

7. Ionic size When a nonmetal gains e -, anion is larger than neutral atom

8. questions How can we predict that oxygen will form an O 2- ion and not an O 3- ion? Predict the formula for an ionic compound formed from the following elements: Mg, S K, Cl Cs, F Ba, Br Why are cations smaller than their parent atoms ? Why are anions larger?

9. Metallic bonding Metals are ATOMIC SOLIDs that form crystals (network of atoms) What holds atoms together? “Electron Sea” model - atoms in sea of valence electrons Electrons shared amongst all atoms

10. dipole -dipole attraction The attractive force between the positively charged end of one polar molecule and the negatively charged end of another molecule

11. HYDROGEN BONDING Strong dipole-dipole attraction Occurs between molecules in which H is bound to very electronegative atom such as F, O, and N Strong attraction due to polarity and due to small size of H atom (allows close approach by positive dipole)

12. London dispersion forces weak forces resulting from temporarily uneven distribution of e- induces a dipole in a neighbor between atoms and non-polar molecules

13. Lewis structures

14. Objectives - Lewis structures To Learn to Write Lewis Structures Using Knowledge of Electron Configurations To Learn to Write Lewis Structures for Molecules with Multiple Bonds

15. What is a lewis structure? Representation of molecule or polyatomic ion showing how valence e - arranged among atoms Only show valence e - since these are ones participating in bonding e - shown as dots

16. Lewis structure - ionic compound No dots shown around Na, since it gives up its 1 valence e - Cl shown with 8 valence e -, since it gains 1 e - Charges on ions shown outside of brackets

17. Lewis structures - covalent bonds Hydrogen wants duet (2) of e - H · · H H : H

18. Lewis structures - covalent bonds Fluorine wants octet (8) of e - Shares pair of e - with another Fluorine atom to make F 2

19. Lewis structures - terminology Electron pair between two atoms = bonding pair Electron pairs not between two atoms = unshared pairs or lone pairs Each fluorine has 1 shared pair and 3 lone pairs

20. Tips for writing lewis structures Include all valence e - from all atoms Total # of e - = sum of all valence e - from atoms in molecule Bonded atoms share 1 or more e - pairs Arrange e - so each atom surrounded by enough e - to fill valence orbitals (usually octet; duet for Hydrogen)

21. Lewis structure steps Find sum of valence e - of all atoms in molecule example H 2 O H has 1 valence e - O has 6 valence e - 1 + 1 + 6 = 8 valence e- in H 2 0

22. Lewis structure steps Use one pair e - for bond between each pair of bound atoms. A line can can be used to represent a pair of e - H - O - H

23. Lewis structure steps Arrange remaining e - to satisfy duet rule for H and octet rule for other atoms Note: two lone pairs on oxygen atom

24. Questions Write Lewis structures for each of the following molecules: CCl 4 PH 3

25. Lewis structures for molecules with multiple bonds Example - CO 2 Count valence e - : Carbon has 4, Oxygen has 6 4 + 2(6) = 16 valence e - Show bonds between C and the Oxygens: O - C - O

26. Lewis structures for molecules with multiple bonds O - C - O Distribute remaining e- (16 - 4 = 12 e-) to achieve noble gas config Put two pairs between C and each O so C has noble gas configuration

27. Single bonds, double bonds, Triple bonds Single bond: 1 pair e - shared by atoms Double bond: 2 pair e - shared by atoms Triple bond: 3 pair e - shared by atoms

28. Resonance structures A condition occurring when more than one VALID Lewis structure can be written for a molecule Shows limitations of bonding models we have developed

29. Question Write lewis structures for following molecules: HF N 2 NH 3 CH 4 SO 3

30. Lewis Structure Hydrogen Fluoride 1 + 7 = 8 valence e- H - F Distribute remaining 6 valence e- 3 lone pairs on F

31. Lewis structures N 2 Diatomic Nitrogen Molecule 5 + 5 = 10 valence e - N - N Distribute remaining 8 valence e -

32. lewis Structures NH 3 Ammonia 5 + 3(1) = 8 valence e - H - N - H | H Distribute remaining 2 e -

33. lewis Structures CH 4 Methane 4 + 4(1) = 8 valence e - H | H - C - H | H No remaining e - to distribute

34. lewis Structures SO 3 Sulfur trioxide 6 + 3(6) = 24 valence e - O - S - O | O 24 - 6 = 18 remaining e - to distribute No ONE way to do it = resonance structure!