This lecture covers the coordination chemistry of chromium bromide hydrates, focusing on the structures and properties of various chromium complexes with different ligands and hydration levels. The instructor explains the nomenclature and coordination numbers of these complexes, highlighting the importance of water molecules in the coordination sphere and the concept of hydration. The lecture also discusses the role of hydrates in solvating the coordination complexes and emphasizes the need to determine the number of water molecules per complex for proper hydration assessment.