Lewis diagram for NO3- and NH4+
The board doesn't allow us to draw diagrams but here are some sites that have what you want.
http://www.google.com/search?q=Lewis+diagram+NO3^-&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a
http://www.google.com/search?q=Lewis+diagram+NH4^%2B&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a