This topic builds on Topic II and aims at broadening students’ knowledge and concepts of bonding and structures of substances. By learning the concept of electronegativity difference between atoms in covalent bonds, students should be able to identify the polar molecules and their partial charges. The knowledge of bond polarity will in turn assist students in understanding the different natures of intermolecular forces.

Students should also be able to understand the origins, natures and strengths of hydrogen bonding, and differentiate van der Waals’ forces in non-polar and polar covalent substances. With the knowledge of various intermolecular forces, they will be able to explain the properties of some molecular crystals such as ice and C60 in terms of their structures. In addition, students will learn more about molecular substances such as the shapes and the non-octet structures of some covalent molecules.