Question

When copper is dissolved in nitric acid, a brown gas (NO2) is evolved, either by direct production of NO2 or by production of NO which is oxidized to NO2 by O2. Provide a Lewis drawing and resonance structures for the nitrate anion.

Answer 1

It is next to impossible to draw Lewis dot structures on this board due to spacing problems.
Put N on a piece of paper. Place three O atoms top, left, and right of the N. You have 24 electrons to add. Do them this way.
To the top O, a pair of electrons on the left side, a pair on top, a pair to the right, and two pair below (between the O and N which makes that one a double bond). To the O on the left of the N, a pair on the left, a pair on top, a pair on the bottom, and a pair between O and N (a single bond there). To the O on the right of the N, a pair between N and O, a pair on top, a pair on bottom, and a pair on the right. That is one structure. To draw the resonance structure, just rotate the double bond between N and the other O atoms. Here is a web site that does a fairly good job of showing what NO3^- looks like. Scroll down the page about half way.
http://www.science.uwaterloo.ca/~cchieh/cact/c120/dotstruc.html

Answer 2

Here is another site. Scroll about half way down the page.
http://eppe.tripod.com/chembond.htm

Answer 3

Thanks Doc