12.1: Introduction 12.2A: Wave Behavior (Worksheet) In the early 20th Century, our understanding of light and matter was progressing very quickly, but some things still didn't make sense to people. Things really started to click when a number of physicists started thinking about things in a different way. One of the revolutionary things they did was to treat seriously, with mathematical equations, the wave nature of light and matter. 12.2B: Dihydrogen (Worksheet) 12.3: Lessons from Dihydrogen 12.4: Sigma Bonding with P Orbitals 12.5: Pi Bonding with P Orbitals 12.6A: Assembling the Complete Diagram 12.6B: Electron Population 12.7: Experimental Evidence 12.8: Symmetry & Mixing At first, we approximated and said that only orbitals of the same kind can interact with each other: s orbitals with s orbitals, px orbitals with px orbitals, and so on. One of the qualitative differences between a real MO calculation and our scrap-paper approach is that mixing does occur between different kinds of orbitals. However, restrictions still apply. 12.9: Bonding Between Different Atoms 12.10: S and P Mixing in HF 12.11: Polyatomic Geometry and Symmetry 12.12: Approximations in Complicated Structures 12.13: Building MO from Smaller Pieces 12.14: Delocalization: Conjugation in Ozone 12.15: Polyenes: Delocalization in Polyenes 12.16: Aromatics 12.17: Heteroaromatics 12.18: Frontier Orbitals 12.19: Solutions to Selected Problems