Formation of Covalent Bonds
- Non-metal atoms can share electrons with other non-metal atoms to obtain a full outer shell of electrons
- When atoms share pairs of electrons, they form covalent bonds
- Covalent bonds between atoms are very strong
- When two or more atoms are covalently bonded together, they form ‘molecules’
- Covalently bonded substances may consist of small molecules or giant molecules
- Weak intermolecular forces exist between individual molecules
- E.g. Each liquid water molecule consists of two hydrogen atoms covalently bonded to an oxygen atom, and in between two individual water molecules there are weak intermolecular forces
- Shared electrons are called bonding electrons and occur in pairs
- Electrons on the outer shell which are not involved in the covalent bond(s) are called non-bonding electrons
- Simple covalent molecules do not conduct electricity as they do not contain free electrons
Diagram showing covalent bonding in a molecule of chlorine (Cl2)
Exam Tip
A key difference between covalent bonds and ionic bonds is that in covalent bonds the electrons are shared between the atoms, they are not transferred (donated or gained) and no ions are formed.