If Ion X has a charge of 2+ and Ion Y has a charge of 1-, the chemical the formula of the ionic compound?

XY2 the 2 must be a subscript

XY2 for a compund, the overall charge must be 0 as X has +2 then Y should have -2. which can only occur when we have 2Y ions

Roman numerals are used in the naming of metallic cations because certain metals are capable of having different charges in ions. For example, iron can have either a 2+ or 3+ charge and Roman numerals are used to differentiate between the two. So Iron (II) Bromide would have the molecular formula of FeBr2 while Iron (III) Bromide would have the chemical formula of FeBr3. Cobalt (II) Phosphate would have the chemical formula of Co3(PO4)2 Your naming of CuBr2 is correct. When trying to name ions be sure to find the charge the of the metal so that you can properly assign its charge using numerals. When trying to write the chemical formula of an ion, first think of the charges of both the cation and the anion. Then assign subscripts to both the anion and cation so that the charge of ion is zero.

XY2 for a compund, the overall charge must be 0 as X has +2 then Y should have -2. which can only occur when we have 2Y ions