<Li> Satisfy the octet rule . Both oxygen atoms currently have 8 electrons assigned to them . The nitrogen atom has only 6 electrons assigned to it . One of the lone pairs on an oxygen atom must form a double bond, but either atom will work equally well . Therefore, there is a resonance structure . </Li> <Li> Tie up loose ends . Two Lewis structures must be drawn: Each structure has one of the two oxygen atoms double - bonded to the nitrogen atom . The second oxygen atom in each structure will be single - bonded to the nitrogen atom . Place brackets around each structure, and add the charge (−) to the upper right outside the brackets . Draw a double - headed arrow between the two resonance forms . </Li> <P> Chemical structures may be written in more compact forms, particularly when showing organic molecules . In condensed structural formulas, many or even all of the covalent bonds may be left out, with subscripts indicating the number of identical groups attached to a particular atom . Another shorthand structural diagram is the skeletal formula (also known as a bond - line formula or carbon skeleton diagram). In a skeletal formula, carbon atoms are not signified by the symbol C but by the vertices of the lines . Hydrogen atoms bonded to carbon are not shown--they can be inferred by counting the number of bonds to a particular carbon atom--each carbon is assumed to have four bonds in total, so any bonds not shown are, by implication, to hydrogen atoms . </P> <P> Other diagrams may be more complex than Lewis structures, showing bonds in 3D using various forms such as space - filling diagrams . </P>

What does each dot in a lewis dot structure represent