1. Covalent bonding
AH Chemistry Unit 1(b)

2. Potential energy diagram
Bond dissociation energy
Bond length (distance between nuclei at minimum energy)

3. Lewis formulae

4. Dative covalent bonds
Co-ordinate covalent bonds

5. Writing Lewis formulae
Calculate total valence electrons – for ions, add or subtract electrons accordingly
Write skeleton structure – more electronegative atoms usually surround central atom
Distribute electrons to atoms surrounding central atom
Distribute remaining electrons to central atom

6. Examples
SCl2
COCl2
BF4-

7. Resonance structures Represents delocalised bonding
You describe the electron structure of a molecule having delocalised bonding by writing all possible electron-dot formulae

8. Ozone

9. Sulphur dioxide

10. Carbonate ion

11. Exceptions to the octet rule
BCl3
PCl5