1. Science 20S Unit #1 - Chemistry in Action Lesson #6 - Ionic Formulas & Naming

7. Determining Ionic Formulas While sometimes it is easy to determine how many ions come together to form a compound, this is not always the case. Instead of drawing Bohr diagrams there are a series of rules that can be followed to determine the ionic formula.

8. Steps to Writing Chemical Formula 1.Write the chemical symbols of the elements starting with the metal. 2.Write the ionic charge above each symbol. 3.Crisscross the numbers from one symbol to the other making them subscripts. If the subscript is 1 it does NOT have to be written. 4.Reduce the subscripts to the lowest possible form using a common factor.

9. Example Magnesium and Bromine

10. Example Calcium and Oxygen

11. Try Sodium & Nitrogen, Potassium & Selenium

12. Naming Ionic Compounds Naming ionic compounds is fairly easy, only 3 steps. 1. Write the name of the metal. 2. Write the name of the non-metal. 3. Change the ending of the non-metal name to ‘ide’.

13. Example MgBr 2 –Magnesium bromide Example CaO –Calcium oxide Example Na 3 N –Sodium nitride

14. Formulas from Names When you are given the name and must determine the formula you follow the same procedure as if you were just given the names of the 2 types of elements.