You would be better of learning some of the formula of molecules that appear in your exam specification (e.g. hydrocarbons) than the whole periodic table. If you do want to learn some of it I would advise the only learning the atoms that appear most often, if you can identify these. Also some of them for which the atomic symbol does not obviously lead to the atom may be worth learning (e.g. Fe-Iron, Au-Gold). Just to point out, there is no obligation to do this as a periodic table, as well as a reactivity series and a list of common ions, is provided (at least for AQA it is).