L3 - Lewis Structures

3.Try drawing the Lewis structure forhydrogen nitrate and the nitrate ion.4. Draw the Lewis Structure forozone, O 3 .You may notice more than one Lewis structurecan be drawn for these species.Notice that two L.S. can be drawncorrectly for ozone, O 3RESONANCEResonance theory, developed by Lewis (1928), is akey component of valence bond theory and ariseswhen no single conventional model using only evennumber of electrons shared exclusively by twoatoms can actually represent the observedmolecule. Resonance involves modeling thestructure of a molecule as an intermediate, oraverage, between several simpler but incorrectstructures.Resonance• One Lewis structure cannot accuratelydepict a molecule such as ozone.• We use multiple structures, resonancestructures, to describe the molecule.• Resonance is denoted by a double headedarrow separating the different LewisStructures:Resonance• But this is at oddswith the true,observed structureof ozone, inwhich……both O—Obonds are thesame length.Resonance• In truth, the electrons that form the second C—Obond in the double bonds below do not always sitbetween that C and that O, but rather can moveamong the two oxygens and the carbon.• They are not localized, but rather are delocalized.4