In this video we'll write the correct formula for Iron (II) acetate (Fe(C2H3O2)2).

To write the formula for Iron (II) acetate we’ll use the Periodic Table, a Common Ion Table, and follow some simple rules.

Because Iron (II) acetate has a polyatomic ion (the group of non-metals after the metal) we'll need to use a table of names for common polyatomic ions, in addition to the Periodic Table.

Keys for Writing Formulas for Ternary Ionic Compounds:

1. Write the element symbol for the metal and its charge using Periodic Table.
2. Find the name and charge of the polyatomic ion on the Common Ion Table (see https://youtu.be/N4N1Njh7nCo).
3. See if the charges are balanced (if they are you're done!)
4. Add subscripts (if necessary) so the charge for the entire compound is zero.
5. Use the crisscross method to check your work.
Notes:

- 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.
Note: It is possible to have two polyatomic ions such as NH4NO3. In this case find and write both names as found on the Common Ion Table.

For a complete tutorial on naming and formula writing for compounds, like Iron (II) acetate and more, visit:

http://www.breslyn.org/chemistry/naming

Drawing/writing done in InkScape. Screen capture done with Camtasia Studio 4.0. Done on a Dell Dimension laptop computer with a Wacom digital tablet (Bamboo).