1. When Atoms Meet
EO4 Bonding

2. Bonds Forces that hold groups of atoms together and make them function
as a unit.
Bonding Forces
Electron – electron
repulsive forces
Nucleus – nucleus
repulsive forces
Electron – necleus
attractive forces

3. Types of Chemical Bonding
1. Metal with nonmetal:
electron transfer and ionic bonding
2. Nonmetal with nonmetal:
electron sharing and covalent bonding
3. Metal with metal:
electron pooling and metallic bonding

4. Three models of chemical bonding
Ionic
Covalent
Metallic
Electron transfer
Electron sharing
Electron pooling

5. Classification of Bonds
Classify the following bonds as ionic, polar covalent,
or covalent: The bond in CsCl; the bond in H2S; and
the NN bond in H2NNH2.
Cs – 0.7
Cl – 3.0
3.0 – 0.7 = 2.3
Ionic
H – 2.1
S – 2.5
2.5 – 2.1 = 0.4
Polar Covalent
N – 3.0
N – 3.0
3.0 – 3.0 = 0
Covalent

6. Electronegativities (EN)
The ability of an atom in a molecule to attract shared electrons to itself
Linus Pauling

7. Classification of Bonds
Difference in EN
Bond Type
Covalent
 2
Ionic
0 < and <2
Polar Covalent
Increasing difference in electronegativity
Covalent
share e-
Polar Covalent
partial transfer of e-
Ionic
transfer e-

8. Polar Covalent Bond
A covalent bond with greater electron density around one of the two atoms H F
electron rich
region
electron poor
region
e- poor
e- rich F H d+ d-

9. Electron density distributions in
H2, F2, and HF.

11. Key Word to work out Polar covalent bond vs pure covalent/non-polar
Dipole moment and symbols
Electronegativity (delta Xp)

13. Practice
Complete electronegativity difference worksheet.

14. Metals and Nonmetals

15. The Octet Rule
Chemical compounds tend to form so that each atom, by gaining, losing, or sharing electrons, has eight electrons in its highest occupied energy level.
The same number of electrons as in the nearest noble gas
The first exception to this is hydrogen, which follows the duet rule.
The second exception is helium which does not form bonds because it is already “full” with its two electrons

16. Ionic Bond - [Ne] 1s22s1 [H] Li+ F Li + F 1s22s22p5 1s2 1s22s22p6 Li+

17. High melting point: strong Intramolecular bonds
Crystal Lattice Structure
Electrostatic attraction between ions

20. Naming Ionics

21. Electrostatic (Lattice) Energy
Lattice energy (E) is the energy required to completely separate one mole of a solid ionic compound into gaseous ions.
Q+ is the charge on the cation
E = k
Q+Q- r
Q- is the charge on the anion
r is the distance between the ions
cmpd
lattice energy
MgF2
MgO
2957
3938
Q= +2,-1
Q= +2,-2
Lattice energy (E) increases as Q increases and/or
as r decreases.
LiF
LiCl
1036
853
r F < r Cl

22. Properties of Ionic Compounds
Volatility is very low (tendency to vaporize)
Electrical conductive in solution and liquid phase but not solid
Solubility is high in polar solvents like water but will not dissolve in non-polar solvents such as hexane
Solvation or
dissociation discuss.

23. Review Ionic Cation + and Anion –
Ions formed by oxidation and reduction to be noble gas
Electrostatic attraction
Lattice structure
High b.p. and m.p.
Low Volalitility
Soluble in water
Molten or dissolved electric conducters

24. Things to Review How is charge on ion predicted?
What are the polyatomic ions (oxyanions)?
What holds an ionic compound together?
How are ionic compounds named?
What is oxidized and reduced? Who gets reduced and who gets oxidized (OIL RIG)
Ionic are called formula units and not molecules!!!

25. Lewis Structures
Developed the idea in 1902.
G. N. Lewis

26. Valence Electrons The outer shell electrons of an atom
Participate in chemical bonding
Group
# of valence e-
e- configuration 1A 1
ns1 2A 2
ns2 3A 3
ns2np1 4A 4
ns2np2 5A 5
ns2np3 6A 6
ns2np4 7A 7
ns2np5
9.1

27. Lewis Dot Symbols

28. Lewis Dot Symbols
Place one dot per valence electron on each of the four sides of the element symbol.
Pair the dots (electrons) until all of the valence electrons are used.
Nitrogen, N, is in Group 5A and therefore has 5 valence electrons. N : . . N : : N . : N .

29. Covalent Bond
A chemical bond in which two or more electrons are shared by two atoms.
How should two atoms share electrons?
7e-
7e-
8e-
8e- F F + F
Lewis structure of F2
Non-polar: Why?
lone pairs F
single covalent bond
single covalent bond F

30. Distribution of electron density of H2

31. Lewis structure of water
single covalent bonds
2e-
8e-
2e- H + O + H O H or
Double bond – two atoms share two pairs of electrons
8e-
8e-
8e-
double bonds O C or O C
double bonds
Triple bond – two atoms share three pairs of electrons
triple bond
8e- N
8e- or N
triple bond

34. Single bond < Double bond < Triple bond
Covalent Bond Energy
The energy required to break a particular bond in one mole of gaseous molecules is the bond energy.
Bond Energy
H2 (g)
H (g) +
436.4 kJ
Cl2 (g)
Cl (g) +
242.7 kJ
HCl (g)
H (g) +
Cl (g)
431.9 kJ
O2 (g)
O (g) +
498.7 kJ O
N2 (g)
N (g) +
941.4 kJ N
Bond Energies
Single bond < Double bond < Triple bond

35. Triple bond < Double Bond < Single Bond
Covalent Bond Lengths
Bond Type
Bond Length
(pm)
C-C
154
CC
133
CC
120
C-N
143
CN
138
CN
116
Bond Lengths
Triple bond < Double Bond < Single Bond

37. Light-Matter Interactions
3 x 1020
3 x 1016
3 x 1012
3 x 108
3 x 104
Frequency in Hz
Dissociation
Ionization
Vibration
Rotation

38. Microwaves p. 102

39. Review Covalent See page 103 Formed between no-metals
Electron pairs are shared.
Electrostatic attraction for shared pair
Called molecules
Lower m.p. and b.p.
Can be volatile
Typically insoluble in water
Do not conduct electricity due to lack of ions

40. Rules for Writing Lewis Structures
Draw skeletal structure of compound showing what atoms are bonded to each other. Put least electronegative element in the center.
Count total number of valence e-. Add 1 for each negative charge. Subtract 1 for each positive charge.
Use one pair of electrons to form a bond (a single line) between each pair of atoms.
Arrange the remaining electrons to satisfy an octet for all atoms (duet for H), starting from outer atoms.
If a central atom does not have an octet, move in lone pairs to form double or triple bonds on the central atom as needed.

41. 5 + (3 x 7) = 26 valence electrons
Write the Lewis structure of nitrogen trifluoride (NF3).
Step 1 – N is less electronegative than F, put N in center
Step 2 – Count valence electrons N - 5 (2s22p3) and F - 7 (2s22p5)
5 + (3 x 7) = 26 valence electrons
Step 3 – Draw single bonds between N and F atoms.
Step 4 – Arrange remaining 20 electrons to complete octets F N

42. 4 + (3 x 6) + 2 = 24 valence electrons
Write the Lewis structure of the carbonate ion (CO32-).
Step 1 – C is less electronegative than O, put C in center
Step 2 – Count valence electrons C - 4 (2s22p2) and O - 6 (2s22p4)
-2 charge – 2e-
4 + (3 x 6) + 2 = 24 valence electrons
Step 3 – Draw single bonds between C and O atoms
Step 4 - Arrange remaining 18 electrons to complete octets
Step 5 – The central C has only 6 electrons. Form a double bond. 2- O C

43. Resonance
More than one valid Lewis structures can be written for a particular molecule
The actual structure of the carbonate ion is an average of the three resonance structures 2- 2- 2- O C - O C - O C -

44. Exceptions to the Octet Rule
The Incomplete Octet
Be – 2e-
2H – 2x1e-
4e-
BeH2 H Be
B – 3e-
3F – 3x7e-
24e-
3 single bonds (3x2) = 6
9 lone pairs (9x2) = 18
Total = 24 F B
BF3

45. Exceptions to the Octet Rule
Odd-Electron Molecules
N – 5e-
O – 6e-
11e- NO N O
The Expanded Octet (central atom with principal quantum number n > 2) S F
S – 6e-
6F – 42e-
48e-
6 single bonds (6x2) = 12
18 lone pairs (18x2) = 36
Total = 48
SF6

46. Lewis Dot Key Terms
Bonding pair of Electrons (Shared pair of electrons) vs. Non-bonding electrons (Lone pair of electrons)
Cation and anion molecules

47. Practice
Complete Lewis-Dot worksheet

48. Not the same as molecular geometry!
Electron Domain Geometry

51. Bond Angles in Molecular Geometry
LP/LP>LP/BP>BP/BP
Why, lone pair occupy more space and create greater repulsion. Think balloon geometry with big and little balloons.

52. VSEPR THEORY
When non-bonded pairs are present it is not possible to know the exact bond angles. These are measured using X-ray crystallography.
No two molecules with lone pairs have the exact same geometry.
Why: differing electronegativity and multiple bonds

53. VSEPR Valence Shell Electron Pair Repulsion \
Electron Domain: region where pairs of electrons exist.
Electron domain geometry vs. molecular shape geometry.

58. Practice Page
Ball and stick model

59. Practice Continued
Add to Lewis Dot the Electron Domain Geometry and Molecular Geometries Use Moleview to create ball and stick models and diagram on Lewis Dot but add lone pairs, also draw 3D diagram.
Electron Domain Geometry, Molecular Geometry (VSEPR), Ball and Stick with lone pairs, 3D diagram.

60. Sart Hybridization