To do well in GCSE Science students should have a good understanding of the fundamental ideas in chemistry. This is the fourth of six quizzes aimed at reinforcing these ideas and it focusses on covalent bonding of atoms in compounds (molecules).
When elements react, atoms of each element join with atoms of other elements to form compounds. The atoms are held together by chemical bonds which can be either ionic or covalent. This quiz is all about covalent bonding. The three covalently bonded compounds that you need to know about in order to pass your exams are water, carbon dioxide and chlorine gas.
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.
Have a go at this quiz and see how well you understand covalent bonding.