That's a shame, I reached an impossible situation. The best chess move is Re5+ which includes the letters Re which is the element Rhenium with atomic number 75. However since the roman numerals need to multiply to 35 then the only valid solution is having VII and V (XXXV for 35 is not recognized for some reason), and V is Vanadium with atomic number 23 and I is Iodine with 53. That already leaves me with 227, above the 200 threshold for one of the rules.

You should be able to do XXXV and I to get 35, I think it needs two roman numerals to multiply (that worked for me at least)