Explain partial charges, with problems, then link this to bond polarity. Explain the differences in arrows 'language'. Draw organic structures as line structures and no stereochemistry (until you discuss that). Make stoichiometry explicit and link the structures to names to build on the concepts.
Re-teach electronegativity quickly because you don't necessarily trust the person who's taught before you. Make sure that it's reiterated, and then follow through to bond polarity and partial charges. Include all of that information first before going on to do reaction mechanisms. So the first thing to do is draw in partial charges to identify the electrophile and the nucleophile before going on to the next step. It's about doing examples all the way from first principles to build up those concepts.
Do many examples, on the projector or board, from first principles. Start with partial charges and identification of the nucleophile and electrophile, then draw in arrows.
Use a lot of demonstrations - actually doing reactions at the front of the class. You can't actually see the electrons moving when you're doing the reaction, but still it helps to use demonstrations. Beware of possible misinterpretations that could arise when doing demonstrations.
When talking about curly arrows and electrons moving, talk about reactions as a trading port for electrons - electron auction - in terms of trying to understand who has got electrons and who wants them.
Use model kits for third year pericyclic reactions: It's visual and it's used every lesson because everything uses the same rule. That's the message to get to them - that you’re not teaching four new things. It's all the same rules. They just move slightly differently. So they see the same models and they can see where the cyclic reactions close. That's very hard to demonstrate in two dimensions. The bigger models are much better as well.
Throw in pop quizzes when you discuss a concept and then give an example and give them a few minutes to work through that example. That's moving towards a partially flipped classroom context. Also use worksheets to give an increased level of formalisation to it.
