1. 8-3 Names and Formulas for Ionic Compounds

2. Objectives Write formulas for ionic compounds and oxyanions
Name ionic compounds and oxyanions

3. Key Terms Formula unit Polyatomic ion Monoatomic ion Oxyanion
Oxidation number

4. Formulas for Ionic Compounds
A formula unit= simplest ratio of ions representing a compound
ALL ionic compounds are written as formula units (not the case for covalent compounds)

5. Monoatomic Ions Monoatomic ions contain a single element
Be2+, Na+, Fe3+
Notice the charge on the elements!

6. Polyatomic Ions
Polyatomic ions have more than one element, with a net charge
SO42-, NH4+, NO2-, C2H3O2-
Treat like a single unit, not individual ions

7. Naming Binary Ionic Compounds
Step 1: Name the cation first and the anion second.
Step 2: Monoatomic cations use the element name.
Step 3: Monoatomic anions use the ion name with the –ide ending.
Step 4: For d-block cations you must write the cation charge as a roman numeral in parentheses.
Step 5: If the compound contains a polyatomic ion, just use the name of the ion.

8. Naming Binary Ionic Compounds
Example:
NaCl: Sodium Chloride
FeO: Iron (II) Oxide
NH4Cl: Ammonium Chloride

9. Writing a Chemical Formula from the Name
Step 1: Write the element symbol for name of the ion
Step 2: Write the charge of the ion
Step 3: If the total charge equals zero, you are done. If the total charge does not equal zero, you must change the subscripts so that the total charge equals zero (‘drop-n-cross’).

10. Writing a subscript for a polyatomic ion: put a parenthesis around it with the subscript on the outside of the parenthesis
Example: Cr(SO4)2

11. Example: Barium Fluoride
Step 1: Ba F
Step 2: Ba2+F-
Step 3: Total charge = +1
Step 4: BaF2

12. Example: Iron (III) Sulfate
Step 1: Fe SO4
Step 2: Fe3+SO42-
Step 3: Total charge = +1
Step 4: Fe2(SO4)

13. Example: Beryllium Oxide
Step 1: Be O
Step 2: Be2+O2-
Step 3: Total charge = 0  BeO

14. Homework
P.227 #35-36,38-39
P.237 #74-79