Chemical Bonding and Molecular Structure

This chapter explains the forces that hold atoms together in molecules, known as chemical bonds. It begins with the fundamental reasons atoms combine, focusing on achieving stable electron configurations as described by the octet rule. You will learn to draw Lewis structures to represent electron sharing in covalent bonds and understand the formation of ionic bonds through electron transfer. The chapter also introduces concepts like formal charge and discusses exceptions to the octet rule.

The focus then shifts to predicting the three-dimensional shapes of molecules. The Valence Shell Electron Pair Repulsion (VSEPR) theory provides a model for determining molecular geometry based on minimizing repulsion between electron pairs. To explain the nature of covalent bonds in more detail, the chapter introduces Valence Bond Theory (VBT), which describes bond formation as the overlap of atomic orbitals. A key part of VBT is the concept of hybridization, which explains the observed geometries of molecules like methane and ethene.

A more comprehensive model, Molecular Orbital Theory (MOT), is presented to explain properties that VBT cannot, such as the magnetic behaviour of oxygen. You will learn to construct molecular orbital diagrams for simple diatomic molecules to calculate bond order and predict stability. The chapter also covers bond polarity, dipole moments, and the important intermolecular force of hydrogen bonding. The most difficult concepts are usually hybridization and MOT. A strong understanding of electronic configurations from the chapter "Structure of Atom" is essential.