Writing Ionic Formulas from Names

Steps for Writing Ionic Formulas from Names Write the formula for the cation (metal) including the charge Write the formula for the anion (non-metal or polyatomic ion) including the charge Use the criss cross method to balance the charges.

Examples 1. Write the formula for Potassium Oxide 2. Write the formula for Tin (II) Chloride *Note: Roman numeral is the charge on the cation Tin (II) = Sn 2+ K + O 2- K2OK2O Sn 2+ Cl - SnCl 2

3. Write the formula for Aluminum Sulfate (note: Sulfate is a polyatomic ion!) 4. Write the formula for iron (III) sulfide 5. Write the formula for calcium hydroxide Al 3+ SO 4 2- Al 2 (SO 4 ) 3 Fe 3+ S 2- Fe 2 S 3 Ca 2+ OH - Ca(OH) 2

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Now it’s your turn – write the formula from the name 1) Ammonium phosphate cation=NH 4 + anion=PO 4 3- Formula = (NH 4 ) 3 PO 4 2) Iron (II) oxide cation =Fe +2 anion= O -2 Formula = FeO 3) Iron (III) oxide cation = Fe +3 anion= O -2 Formula = Fe 2 O 3

4) Magnesium chloride cation =Mg +2 anion= Cl - Formula = MgCl 2 5) Copper (II) sulfate cation =Cu +2 anion=SO4 -2 Formula = CuSO 4 6) Sodium hydroxide cation =Na + anion=OH - Formula = NaOH

7) Gold (III) carbonate cation =Au +3 anion=CO 3 -2 Formula = Au 2 (CO 3 ) 3 8) Calcium hydroxide cation =Ca +2 anion=OH - Formula = Ca(OH) 2 9) Strontium iodide cation =Sr +2 anion=I - Formula = SrI 2 10) Aluminum sulfide cation =Al +3 anion=S -2 Formula = Al 2 S 3