Chemical Formula Entry

     While leaning how to figure how to write compounds and formulas most difficult. I asked a  fellow student how they remembered when it is a roman numeral and when it is not. The said that roman numerals are the transition metals, which is the middle of the periodic table this will tell you if it is roman numerals or not, then I look at the subscript and that tells you what roman numeral it is.  When looking for the charges the second elements charge goes to the first element subscript and the first element charge, if they have one and is not canceled it goes to the second element for its subscript.