1. 3 Types of Bonds Ionic Covalent Metallic
Which atoms/ions make these bonds?
How do bonds form (share or electrostatics)?

2. Ionic Properties? States of matter?
Ease of formation depends on ? and ?
Draw Lewis dot structures to represent formation of ionic bonds (electrostatic attraction)
Do NaCl
Try CaCl2

3. Electrostatics → Lattice Structure
Coulomb Forces very important
To make lattice, try to maximize ________________ and minimize ________________

4. Lattice Energy Energy to ??? Endo or exo?
What would influence lattice energy?
Think Coulomb
Arrange NaF, CsI, and CaO in order of increasing lattice energy. Explain your order.

5. Compound
Lattice Energy (kJ/mol)
LiF
1030
MgCl2
2326
LiCl
834
SrCl2
2127
LiI
730
NaF
910
MgO
3795
NaCl
788
CaO
3414
NaBr
732
SrO
3217
NaI
682 KF
808
ScN
7547
KCl
701
KBr
671
CsCl
657
CsI
600

6. Covalent Bonding How are these bonds made?
Properties? States of Matter?
Structure-Do you expect lattice structures?

7. Structure is Molecular or Network

8. Lewis Dot Diagrams
For each of the following, a. Draw the Lewis structure b. Does it obey octet rule? Does it have to? c. Name it CH4, H2O, N with F, BH3, PCl5, CO2, N2, CO Why can B have CN=3? Why can P expand? Why can N2 make triple? Bond length of CO vs CO2?

9. Do we always have equal sharing?
Review
Polarity ( charge), Dipole moment ()

10. 0-0.4: nonpolar covalent
: slightly polar
: polar
> 2: ionic
Which bond is more polar and draw the dipole moment?
S-Cl, S-Br, Se-Cl, or Se-Br
B-Cl or C-Cl

11. Cl-F
 = 0.88 D
Bond length = 1.63 Å
Does the small  value make sense?
Which atom is expected to be -? Which +?
Draw

12.  = Qr Q = electron charge r = bond length
Make sense?
Cmpd
r (Å)
 Pauling
 (D) HF
0.92
1.9
1.82
HCl
1.27
0.9
1.08
HBr
1.41
0.7
0.82 HI
1.61
0.4
0.44

13. Summary Ionic M with NM High mp Brittle Lattice structure
Electroneg diff > 2.0
Ionic Solids = non-conductive
Covalent
NM’s only
Low mp
Molecular (few network solids)
Polarity ( )
Some trans M salts can be covalent (next slide)

14. Trans M Salts: Ionic or Cov? Depends on oxid state of Metal
MnO Mn2O7
green solid green liq
mp = 1842oC fp 5.9oC
What is oxid state of Mn in each cmpd? Name each cmpd.
Based on Pauling scale, what is expected? Mn = 1.5; O = 3.5
Look at props, what do you think?
Trend? (side note: cut off is usually +4)

15. Try This Cmpd A is a yellow solid whose mp = 41oC
Cmpd B is a green solid whose mp = 2320oC
Match them to Cr2O3 and OsO4

16. Lewis Structures ctd. Use valence e-
Central atom: least amt or least electroneg
Octet Rule (C, N, O, F)
Must also consider
Resonance (Draw ClO2- ) (Name of this ion?)
Formal Charge
least amt FC or negative FC on most electroneg atom
Which resonance form is energetically most favorable?

17. Try SCN- There are three resonance forms
Draw them and pick the best one
Try Ozone, O3
2 or 3 resonance forms?
Would you expect two different bond lengths?
In reality, only get one (in between single and double). Why?
Discuss resonance and partial double bond character

18. Common Examples
Polyatomics with O show resonance and partial bond character
Examples?
Benzene, C6H6 =

19. Bond Enthalpy, H
Bond enthalpy is the energy needed to break covalent bonds (lattice E = E to break lattice)
For ex,
Cl2 → 2 Cl H = 242 kJ/mol
Does + value make sense?
What does this # mean? Translate/sentence
C-H has H = 413 kJ
What is the overall energy to break up methane? CH4 → C + 4H

20. Draw Lewis for O2 and H2O2
Compare the O to O bond strength in each compound.
One has H=495 kJ; the other has H=146 kJ. Which is which?
Which would be more reactive?

21. Use Bond Enthalpies to find Hrxn
Hrxn =  H bonds broken -  H bonds made Ex. 2 C2H6 + 7 O2 → 4 CO2 + 6 H2O
ANS: kJ
Does negative make sense?
Explain the # in words.
Name of C2H6?