Resources

Learning to Name and Write Formulas:

- Determining the type of compound you are working with.

- Applying the rules for naming or formula writing for that type of compound.

- Practicing until it becomes second nature.

How to Name Ionic Compounds with Polyatomic Ions

Ternary ionic commpounds are made up of a metal and a polyatomic ion. Be sure you can identify the type of compound before naming or writing formulas!

• Name the metal (usually the the first element in the formula) as it appears on the Periodic Table.
• K⁺ = Potassium    Ca²⁺ = Calcium    Al³⁺ = Aluminum
• Use the Common Ion Table to write the name for the polyatomic ion.

• Occasionally there will be two polyatomic ions (e.g., NH₄NO₃). Here you write both names as found on the Common Ion Table.

It’s helpful to memorize some of the more important polyatomic ions to make your naming and formula writing quicker and more effective. This video, how to memorize polyatomic ions should help you accomplish this goal.

Note that when we write the names and formulas for compounds, most of the Polyatomic ions have negative charges. The exception is the ammonium ion, NH₄⁺. Watch out for this ion.