Chemistry - Covalent Bonding (AQA)

When covalent chemical bonding occurs, atoms of the elements involved share electrons. Electrons are shared in pairs and atoms can share more than one pair of electrons. When an atom has shared the exact number of electrons it requires, it will not be able to share with any other atoms. No electrons are lost or gained therefore covalent compounds do not contain ions, they are made up from molecules. This is very different to ionic compounds which are giant structures of ions.

Some molecules are very simple and consist of only two atoms, like the oxygen that we breathe. Others are incredibly large and complex for example, a single strand of human DNA is made up from around 200 billion atoms, all covalently bonded.

It is essential for the exam that you know the about atoms, molecules, elements and compounds. A lot of students are not sure how these are all related.

• All matter is made from atoms
• Molecules are made from covalently bonded atoms of non-metals
• Non-metal elements are usually made from molecules
• Metal elements are always made up from atoms, never molecules
• Compounds are made from different atoms joined together
• Compounds made from non-metal atoms joined together are always made of covalent molecules

Have a go at this quiz and see how well you understand covalent bonding.