Syllabus     |   |    Next Section

Learning Plan

  1. Watch the video on writing formulas for ionic compounds with polyatomic ions.

  2. Review Essential Information on formula writing for compounds with polyatomic ions.

  3. Correctly write the formula for ten simple ionic compounds in a row!

Once you get ten in a row, return to the Syllabus or continue to Cumulative Practice #2.

Essential Information

  • Write the element symbol for the metal and its charge using Periodic Table.
  • Find the name and charge of the polyatomic ion on the Common Ion Table.
  • See if the charges are balanced (if they are you're done!)
  • Add subscripts (if necessary) so the charge for the entire compound is zero.
  • Use the crisscross method to check your work.
  • Don’t write the subscript '1'.
  • If you use the criss-cross method and end up with something like Ca2S2 you'll need to reduce the subscripts to Ca1S1 which we write CaS.