There is actually some decent chemistry being explained in Breaking Bad.
I assume they had some chemistry consultant on set to write things on the board and proof the explanations that Walter was giving to his class.
Admittedly, Walter is portrayed as a pretty awful teacher who has some really interesting things to say about a subject that he finds fascinating. I'm hopeful I'm a little more engaging with my students much of the time, but I fear that sometimes I come off a bit like Walter White in the classroom.