 When covalent bonds form, the atomic orbitals overlap forming two types of molecular orbitals
 When two atomic orbitals overlap along the bond axis (head on), a sigma bond is formed
 This bond involves s-atomic orbitals, p(x)-atomic orbitals and the combination s and p(x) orbitals
 All single bonds are sigma bonds
 When two p-atomic orbitals overlap sideways , a pi bond is formed
 The second (in a double bond) and third bond (in a triple bond) between two atoms are pi bonds
 The electrons involved in pi-bonds are sometimes able to spread between different bonding positions. This is called delocalization of electrons.
 The delocalization of electrons gives stability to the structure
 You can represent this idea using resonance structures .
 Benzene displays a special ring structure due to the delocalization of the electrons.
 The formation of covalent bonds often starts with the excitation (gaining energy) of the atom.
 Atoms are able to form stronger covalent bonds using hybrid orbitals
 Hybrid orbitals form when atomic orbitals mix to produce orbitals of intermediate energy
 The idea of hybridization is used to explain why methane (CH4) has 4 identical C-H bonds.
 The shape of hybrid orbitals is found on www.heinemann.co.uk/hotlinks
 The idea of hybridization can also be used to explain the shape of molecules