1. Types of covalent bonds

2. Electronegativity & bond type
The difference in electronegativity decides the type of bond.
Ionic – Difference is > 2.0
Polar – Difference is > 1.4 but < 2.0
Non-polar – difference is < 1.4

3. Ionic
Large electronegativity difference results in one atom taking the electron.
MgO Mg is + & O is – so they stick together

4. Non- polar bonds
Shared pair of electrons is shared equally by each atom.
Shared electrons are equally between each atom
No partial charges exist
Eg. F – F Cl - Br

5. Polar bonds
The shared electrons are closer to one atom than the other so are not in the middle.
Like a tug-o-war where the stronger electronegative atom wins.
The atom with greater electronegativity pulls the shared electrons closer to it.
Eg. C-F Which has a stronger “pull” on the electrons?
The F atom is slightly negative because the electrons are closer to it.
The C atom is slightly positive because the electrons are farther from it.
Unequal sharing of electrons produces partial charges in a molecule (poles).

6. Polarity
Polarity exists if a molecule has charged poles (opposite ends)
These molecules are attracted to other molecules with a charge.
The more similar the polarities are the easier the two substances mix.

7. Polarity & shape
A molecule can have polar bonds & be a polar molecule.
Eg. Who’s sort of negative & sort of positive?
 S-O H-Cl C-O
 A molecule can have a polar bond & NOT be a polar molecule.
 Eg. CO2 O-C-O
 Both oxygens pull equally & cancel each other out so there is no polar end.
 The shape of a molecule can affect whether a molecule is polar. Polar bonds can cancel each other out.

8. Ionics dissolve in water
The polarity of water explains the fact that ionic compounds dissolve in water. The charges of the ions in the ionic bond are attracted to the polar ends of water (the “sort of” negative & “sort of” positive charges).