This is the first part of sub-topic 4.3 Covalent structures. It includes Lewis structures, the "octet rule, resonance hybrids and giant covalent structures. I have not included VSEPR theory to determine the shapes of simple molecules and ions on this page. Since the underlying theory is the same for 2, 3, 4 and 5 and 6 electrons pairs around the central atom I have prepared a separate page on VSEPR theory as 5 and 6...