Chemical Bonding

This chapter discusses fundamental aspects of chemical bonding in molecules, highlighting the difference between the physical mechanism of bond formation and bonding models. The historical development of the most important bonding models is critically discussed, and the current understanding of the nature of chemical bonding is presented. The crucial importance of orbital symmetry for the structure and reactivity of molecules is emphasized. Further topics concern the length and strength of a chemical bond, the difference between the electron-sharing bond A–B and the dative bond A→B as well as the nature of polar bonds. The difference between the bond formation process between the original fragments A and B, which takes into account the deformation of the electronic structures, and the description of the bond finally formed, which is often confused and leads to controversy, is emphasized. A few selected model compounds are analyzed using modern methods of bond analysis to demonstrate the advances in sophisticated bond analysis that have been made. They illustrate the differences in chemical bonds between the main group atoms of the first octal row of the periodic table and the heavier homologs, as well as the transition metals (TMs).