Chemical Bonding Ionic and Covalent Bond

1
Chemical Bonding Ionic and Covalent Bond
0
.
2
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
0
9.1
3
0
9.1
4
0
A covalent bond is a chemical bond in which two
or more electrons are shared by two atoms.
Covalent bonds are exothermic.
Lewis structure of F2
9.4
5
Lewis structure of water
0


Double bond two atoms share two pairs of
electrons
or
Triple bond two atoms share three pairs of
electrons
or
9.4
6
Polar covalent bond or polar bond is a covalent
bond with greater electron density around one of
the two atoms
0
electron rich region
electron poor region
e- rich
e- poor
d
d-
9.5
7
Electronegativity
0

• 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
0
The bond that results from the electrostatic
attraction between positively charged cations and
negatively charged anions. Ionic bonds are
exothermic.
1s22s1
1s22s22p5
1s2
1s22s22p6
He
Ne
9.2
9
0
10
0
9.5
11
Classification by difference in electronegativity
0
ionic character
Bond Type
0 - 5
Nonpolar Covalent
? 50
Ionic
5 gt and 50
Polar Covalent ionic character Highest
lowest/highest x 100
9.5
12
0
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
0

1. 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
2. Count total number of valence e-. Add 1 for each
   negative charge. Subtract 1 for each positive
   charge.
3. Complete an octet for all atoms except hydrogen
4. If structure contains too many electrons, form
   double and triple bonds.

9.6
14
0
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- ?
3 single bonds (3x2) 10 lone pairs (10x2)
26 valence electrons
9.6
15
0
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-
9.6
16
0
The enthalpy change required to break a
particular bond in one mole of gaseous molecules
is the bond energy.
Bond Energy
9.10
17
Average bond energy in polyatomic molecules
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 Na1 1
• O-2 -2 F 0

20
LEO goes GERLose electron it is oxidationGain
electron it is reduction