Define a resonant bond structure. Show examples of how a double bond may exist as a resonant structure. Draw structural diagrams for ozone and sulfur trioxide. Determine that the double bond can resonate between oxygen atoms in ozone and oxygen atoms and the principle sulfur atom in sulfur trioxide. Present a co-ordinate covalent bond structure, ammonium chloride, and outline the co-ordinate covalent bond structure. Define a co-ordinate covalent bond.