1. The problem statement, all variables and given/known data Arrange the nitrogen atoms of histamine in order of their decreasing basic strength. http://img134.imageshack.us/img134/7339/histamine.th.jpg [Broken] 2. Relevant equations The more ready the nitrogen atoms donate lone pair, the greater the basicity; 3. The attempt at a solution The rightest one must be the most basic. But how about the other two? It must be related to resonance. But I just don't know how to work out the answer by drawing the resonance structure (how to draw this one~?) * one more simple question: when a metal ion (say Cu2+) forms a complex with EDTA, what is the coordination no.? (count the no of ligand - 1 or the dative bond - 6 ?) Thanks!