1. Chemical Bonding Ionic and Covalent Bond
Chemical Bonding Ionic and Covalent Bond .

2. Group # of valence e- e- configuration 1A 1 ns1 3A 3 ns2np1 5A 5
Valence electrons are the outer shell electrons
of an atom. The valence electrons are the
electrons that particpate in chemical bonding.
Kernal is the rest of the atom
Group
# of valence e-
e- configuration 1A 1
ns1 3A 3
ns2np1 5A 5
ns2np3 7A 7
ns2np5
9.1

3. 9.1

4. A covalent bond is a chemical bond in which two or more electrons are shared by two atoms. Covalent bonds are exothermic.
7e- F F +
7e-
8e- F
8e-
Lewis structure of F2
lone pairs F
single covalent bond
single covalent bond F
9.4

5. Lewis structure of water
single covalent bonds H + O + H
2e- O H or
8e-
2e-
Double bond – two atoms share two pairs
of electrons
8e- O C
8e-
8e- or O C
double bonds
double bonds
Triple bond – two atoms share three
pairs of electrons N or N
triple bond
8e-
8e-
triple bond
9.4

6. Polar covalent bond or polar bond is 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-
9.5

7. Electronegativity
A polar bond is a covalent bond in which the bonding electrons are not shared equally by the two atoms.
Electronegativity is a measure of the ability of an atom to attract the shared e- in a chemical bond.
Polarity is the degree of charge separation of the bond.

8. The Ionic Bond
The bond that results from the electrostatic attraction between positively charged cations and negatively charged anions. Ionic bonds are exothermic.
Li+ F - Li + F
1s22s1
1s22s22p5
1s22s22p6
[He]
1s2
[Ne]
9.2

10. 9.5

11. Classification by difference in electronegativity
% ionic character
Bond Type
0 - 5
Nonpolar Covalent
 50
Ionic
Polar Covalent
% ionic character =Highest –lowest/highest x 100
5 > and ≤50
Increasing difference in electronegativity
Non polar Covalent
share e-
Polar Covalent
partial transfer of e-
Ionic
transfer e-
9.5

12. Cs – 0.7 Cl – 3.0 Ionic H – 2.1 S – 2.5 Polar Covalent Covalent
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
Ionic
H – 2.1
S – 2.5
Polar Covalent
Covalent
N – 3.0
N – 3.0
9.5

13. Writing Lewis Structures
Draw skeletal structure of compound showing what atoms are bonded to each other. Put least electronegative element in the center. Hydrogen cannot be in the center
Count total number of valence e-. Add 1 for each negative charge. Subtract 1 for each positive charge.
Complete an octet for all atoms except hydrogen
If structure contains too many electrons, form double and triple bonds.
9.6

14. 5 + (3 x 7) = 26 valence electrons
Write the Lewis structure of nitrogen trifluoride
Step 1 – N is less electronegative than F,
put N in center
Step 2 –count valence electrons N - 5 and F - 7
5 + (3 x 7) = 26 valence electrons
Step 3 – Draw single bonds between N and F
atoms and complete octets on N and F atoms.
Step 4 - Check, are # of e- in structure equal to number of valence e- ? F N
3 single bonds (3x2)
+ 10 lone pairs (10x2) =
26 valence electrons
9.6

15. 4 + (3 x 6) + 2 = 24 valence electrons
Write the Lewis structure of the carbonate ion
Step 1 – C is less electronegative than O,
put C in center
Step 2 – Count valence electrons C - 4 and O-6
-2 charge – 2e-
4 + (3 x 6) + 2 = 24 valence electrons
Step 3 – Draw single bonds between C and O
atoms and complete octet on C and O atoms.
Step 4 - Check # of e- in structure
3 single bonds (3x2) + 10 lone pairs (10x2) =
26 valence electrons
Step 5 - Too many electrons,
form double bond and
re-check # of e- O C
9.6

16. Single bond < Double bond < Triple bond
The enthalpy change required to break a particular bond in one mole of gaseous molecules is the bond energy.
Bond Energy
H2 (g)
H (g) +
DH0 = 104 kcal
HCl (g)
H (g) +
Cl (g)
DH0 = 103 kcal
O2 (g)
O (g) +
DH0 = 119 kcal O
N2 (g)
N (g) +
DH0 = 226 kcal N
Bond Energies
Single bond < Double bond < Triple bond
9.10

17. Average bond energy in polyatomic moleculesOH H + O
DH0 = 111 kcal
9.10

18. Using the bond energies from pg 131 in the chemistry books, what is the bond energies for the following compounds?
CH4 H2O
CCl4 N2
HBr O2

19. Oxidation numbers match the charge of an item.
Examples:
Cl 0 Na+1 1
O F 0

20. LEO goes GER Lose electron it is oxidation Gain electron it is reduction