Put it this way - if you haven't got A-level chemistry, then the list of symbols for the chemical elements at the back of the Collins dictionary may well come in very useful!
Can you give me an example of how this works in the crossword....you can find element symbols in loads of clues...eg "Li" in Livewires, "In" in intrepid, "Ru" rubicond etc.....or am I missing something obvious?