The AP Chemistry Thread

<p>that's a high 4. The exam wasn't too bad, except I made stupid mistakes on a couple FR questions. yea... 1-15 MC was !#%#$.</p>

<p>I understand formal charge. I LOVE that area of Chem. It's a really basic concept; I hope I can explain it, though. :)</p>

<p>You count the electrons that the structure assigns to each atom (the "assigned" charges), versus the valence electrons that each atom truly has (the "formal" charges). Whichever proposed structure has assigned charges that are closest to the formal charges is likely the correct structure.</p>

<p>Formal charge</p>

<p>F.c =valence-(UNSHARED+1/2(SHARED)</p>

<p>For formal charge, don't you want them to come out to be zero to have the right structure? Or am I off on that. I tried to explain it without using it but I did remember it a bit, just not the specifics so I put that down. And do you think they'd give the points if I put 109 degrees or are they unmerciful about it?</p>

<p>i dunno about bond angle. but does the fc mean that structure 1 was correct? cuz i guessed that, lol.</p>

<p>Hmm... I don't know about that whole 1/2 formula.</p>

<p>But yes, you want the difference between assigned and formal to be 0. That would mean the structure is probably correct (according to theory, anyway).</p>

<p>I have no idea how strict the grading can be. If the answer is pretty close, then maybe they might give some points... But I've seen responses for bond structure that had about five different compounds to name, and the person missed only one and got no credit at all. I was surprised.</p>