chemical bonding

1. Intermolecular Forces
Intermolecular forces are forces between molecules.
Intramolecular forces hold atoms together in a molecule.
Example: ionic, covalent, and metallic.

2. Electronegativity is the ability of an atom to attract
toward itself the electrons in a chemical bond.
Electronegativity - relative, F is highest
H F
electron poor
region
electron rich
region

3. H F
d+ d-

4. e-
e-
δ
- δ
+
2
+
e-
e-
2
+
e-
e-
2
+
e-
e-
δ
- δ
+
2
+
e-
e-
δ
- δ
+
2
+
e-
e-
δ
-
δ
+
2
+
repel attract
e-
e-
2
+

5. Types of Intermolecular Forces
Dipole-Dipole Forces
Attractive forces between polar molecules
Orientation of Polar Molecules in a Solid

6. Dipole – Dipole Forces
d+ d-
d+ d-
d+ d-
d+ d-
d+ d-

7. Types of Intermolecular Forces
Ion-Dipole Forces
Attractive forces between an ion and a polar molecule
Ion-Dipole Interaction

8. Ion – Dipole Forces
Exist when we dissolve an ionic compound in a polar solvent, like H2O.
The d- end of H2O is attracted to a cation (+).
The d+ end of H2O is attracted to an anion (-).

9. Types of Intermolecular Forces
Dispersion Forces – van der Walls forces/London forces
(weakest)
Attractive forces that arise as a result of temporary
dipoles induced in atoms or molecules
ion-induced dipole interaction
dipole-induced dipole interaction

10. Hydrogen Bonding
Hydrogen Bond = an attraction
between a slightly positive hydrogen
atom and a slightly negative atom,
often oxygen or nitrogen

11. Hydrogen Bonding

12. O
H H
δ
+
δ
+
δ-
O
H H
δ
+
δ
+
δ-
O
H H
δ
+
δ
+
δ-
O
H H
δ
+
δ
+
δ-
O
H H
δ δ
+
δ-
hydrogen bonds

13. • A hydrogen bond is an intermolecular
bond.
F—H
O—H
N—H
• A hydrogen bond is formed between
polar molecules that contain hydrogen
covalently bonded to a small, highly
electronegative atom: F, O, N.

14. hydrogen
bond
covalent
bond
covalent
bond
A dipole-dipole bond bond will be formed
between the two molecules which is
called a hydrogen bond.

15. Remember, you need:
A hydrogen atom covalently bonded to an
electronegative atom … N, O or F.
If only one of these conditions is met, you don’t get
hydrogen bonding.
A lone pair of electrons on the electronegative
atom.

16. Coordinate Covalent Bond
• A coordinate bond (also called a dative
covalent bond) is a covalent bond (a shared
pair of electrons) in which both electrons
come from the same atom.
• A coordinate covalent bond is usually shown
with an arrow.

17. Amino-Borane
N has a full
octet an a lone
pair of
electrons.
NH3 is an
uncharged
molecule.
B only has 6
electrons, it is
deficient.
BH3 is an
uncharged
molecule.
N can “donate” its lone
pair to B forming a
co-ordinate bond.

18. Amino-Borane
Now we have a new molecule with a covalent bond between N and B.
While there are formal charges on N and B, the overall charge on the
molecule is neutral.
The bond formed between N and B is just as strong as any covalent
bond.

19. ammonium ion