How can one forget about electronegativity. Yes I have heard the term many times during my studies. Fluorine being the most electronegative. Another concept is resonance, I understand what it is but I am still learning. I get that it lowers the overall energy level. I had a quiz recently to draw up all the resonance forms of a molecule, I think there were 6 and I could only find 3. I still have some learning to do.