1. Chapter 5 is divided in 5 major areas.
Chemical Compounds.
Ionic Bonding.
Covalent Bonding.
Electronegativity.
Shapes of Molecules and Intermolecular forces.

2. Sigma bonds vs Pi bonds Sigma bonds.
A sigma bond is formed when electrons are shared in line with the nuclei. (a head-on overlap of orbitals.)
Pi bonds.
A Pi bond is formed when the shared orbitals are side on i.e. (not in line with the nuclei.)
N.B. Sigma bonds are stronger. In a covalent single bond it is a sigma bond, however, in a double or triple bond there is 1 sigma bond and the others are pi bonds.

4. Polar and Non-Polar Covalent Bonding
A polar bond can be pictured using partial charges:
+ 
H Cl
 = 0.9

5. Inter and Intra Molecular Forces
The force of attraction between ions is stronger than between molecules.
Inter: are forces between molecules.
Intra: are forces within a molecule.
There are 3 kinds of forces that can attract molecules together

6. Van der Waal’s:
These are the weakest forces caused by the movement of e- within a molecule. The electrons move randomly within the bond so at 1 point in time they are nearer to 1 atom than the other. This induces a temporary dipole force.
Temporary dipoles will result in increased boiling points.
The greater number of e- in a molecule the greater the number of temporary dipoles.

7. Dipole-dipole:
The positively charged end of a polar molecule is attracted to the negative end of another molecule.
The dipoles in this case are permanent.
As a result they are stronger than Van der Waal’s forces.

8. Hydrogen Bonding
When H is bonded to F, O or N these elements are sufficiently electronegative to make the bond polar.
H has only 1 e- in its atom, a strong partial positive charge will result.
This means it is very strongly attracted to the negative atom and as a result H2O is a liquid at room temperature with a fairly high boiling point.

9. Shapes of Covalent Molecules

10. VSEPRT
The valence shell electron pair repulsion theory (VSEPRT) states that the shape of a molecule depends on the number of pairs of electrons in the valence shell of the central atom.
Since electrons are negatively charged, the electron pairs repel each other and arrange themselves in space so as to be as far apart as possible.

11. Linear
Beryllium Chloride (BeCl2) has 2 bond pairs of electrons around the central atom.
These bond pairs repel each other as far as possible resulting in a linear shape.
The bond angle is 180o.

12. Triangular planar
Boron trichloride (BCl3) has 3 bond pairs of electrons around the central atom.
The three pairs of electrons repel each other as far as possible resulting in a triangular planar shaped molecule.
The bond angle is 120o.

13. Tetrahedral
Methane (CH4) has 4 bond pairs of electrons around the central atom.
The four pairs of electrons repel each other as far as possible resulting in a tetrahedral shaped molecule.
The bond angle is 109.5o.

14. Pyramidal
Ammonia (NH3) has 3 bond pairs and 1 lone pair of electron around the central atom.
The order of repulsion for pairs of electron is as follows; LP/LP>LP/BP>BP/BP
Therefore the lone pair of electrons in ammonia repel the bond pairs more than the bond pairs repel the lone pair, resulting in a pyramid shaped molecule.
The bond angle is 107o.

15. Planar/V-shaped
Water (H2O) has 2 lone pairs and 2 bond pairs of electron around the central atom.
Since LP/LP>LP/BP>BP/BP the pairs of electron repel each other to result in a V-shaped/planar molecule.
The bond angle is 104.5o.

16. Summary