1. More 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 O2- ion and not an O3- 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. Intermolecular Forces
These are forces between two molecules that determine how they react and interact together

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

12. 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)

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

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. 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

16. 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

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 F2

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 H2O
H has 1 valence e-
O has 6 valence e-
= 8 valence e- in H20

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:
CCl4
PH3

25. Lewis structures for molecules with multiple bonds
Example - CO2
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- ( = 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. Lewis Structure Hydrogen Fluoride 1 + 7 = 8 valence e- H - F
Distribute remaining 6 valence e-
3 lone pairs on F

30. Lewis structures N2 Diatomic Nitrogen Molecule 5 + 5 = 10 valence e-
N - N
Distribute remaining 8 valence e-

31. lewis Structures NH3 Ammonia 5 + 3(1) = 8 valence e- H - N - H | H
Distribute remaining 2 e-

32. lewis Structures CH4 Methane 4 + 4(1) = 8 valence e- H | H - C - H | H
No remaining e- to distribute

33. lewis Structures SO3 Sulfur trioxide 6 + 3(6) = 24 valence e-
O - S - O | O
= 18 remaining e- to distribute
No ONE way to do it = resonance structure!

34. Question Write lewis structures for following molecules: HF N2 NH3 CH4
SO3