What are some common mistakes students make with atomic models?
Forgetting to take them to an exam.
On the desks of very distinguished professors of organic and inorganic chemistry, you would invariably find a set (or sets) of molecular models, with which the prof will continually fiddle.
Why? Because it is hard for all of us to vizualize three dimensional geometry, and to translate that geometry onto two dimensional paper. Models are an aid to this process; and they can be as simple as balls of plasticene and toothpicks. You should ask you prof what sets you can take into an exam, and remember to take them and use them effectively.
PS If you mean atomic models (i.e. electronic structure) rather than molecular models I apologize.