Criss-Cross Method: Writing Ionic Formula Step 1 Symbol for cation (left) then anion (right) Potassium oxide: K O Step 2 Write cation charge K1+ O group 1: loses 1 electron Step 3 write anion charge K1+ O2- group 16: gain 2 electrons Step 4 Check to see if charge = 0 if they don’t crisscross: cation superscript  anion subscript anion superscript  cation subscript   K1+ O2- = 1-  0  K1+ O 2- => K2O Step 5 REDUCE if you can Can’t be reduced

Practice Gallium Oxide 2. Magnesium Phosphate 3. Titanium (IV) Sulfate

4. Rubidum Phosphide 5. Lead (IV) Iodide 6. Ammonium Oxide