Identify the symbol of the cation (first part of the name) and the anion. Identify the valence or charge of each symbol and place it in parenthesis just above the symbol. Cations (Positive Ions). All Group 1 elements in the Periodic Table are +1 in compounds. All Group 2 elements in the Periodic Table are +2 in compounds. Transition elements (have a few charges) will have a Roman Numeral to tell you what positive charge to use. silver is 1+, Zinc is 2+ and Aluminum is 3+. Polyatomic Ions-just use its charge.