1. 3.2 Names and Formulas of Ionic Compounds
Chapter 3 notes

2. Writing Names of Ionic Compounds
1. Name the metal ion
2. Name the non-metal ion by ending the element name with the suffix “ide”
Eg. MgO.....Magnesium oxide
Examples Al2O3 CaF2
Aluminum oxide
Calcium fluoride

3. Writing formulas of Ionic compounds
The positive charges have to balance the negative charges
1. Identify each ion and its charge
e.g Zinc nitride Zn 2+ N3-
2. Determine the total charge needed to balance positive with negative and note the ratio of positive ions to negative ions
e.g = +6 and = -6 so 3 Zn ions and 2 N ions

4. Writing formulas of Ionic compounds
OR use the cross over technique...the charge on the metal becomes the subscript on the non-metal (lose the +) and the charge on the non-metal becomes the charge on the metal (lose the -) ...reduce if needed
e.g. Zn2+ N3- 2+ 3-

5. Writing formulas of Ionic compounds
3. Use subscripts to write the formula. A “1” is not shown. e.g. Zn3N2 Calcium sulphide Ca2+ S2- Ca2S2 (reduce) CaS
Magnesium phosphide
Mg2+ P3-
Mg3P2

6. Nice little summary

7. Multivalent metals (metals with more than one charge...formulas
1. Identify each ion and its charge
e.g. Iron (III) sulphide Fe 3+ and S2-
2. Determine the total charges needed to balance positive with negative and note the ratio of positive to negative ions
e.g = +6 and =-6 so 2 Fe ions and 3 S ions

8. Multivalent metals (metals with more than one charge...formulas
OR use the cross over technique
e.g. Fe S
3. Use subscripts to write the formula
e.g. Fe2S3
Iron (II) chloride
Fe2+ Cl-
FeCl2 3+ 2-
Lead (IV) oxide
Pb+4 O2-
Pb2O4 (reduce)
PbO2

9. Nice easy cHart for Multivalents

10. Names for multivalents
1. Identify the metal e.g. 2. Verify that it can form more than one kind of ion by checking the periodic table or a chart e.g. manganese can be 2+, 3+ or 4+
MnO2

11. MnO2 3. Determine the ratio of the ions in the formula
e.g. 1 manganese for every 2 oxygen
4. Note the charge of the negative ion from the periodic table
e.g. charge on the oxygen is 2-
MnO2

12. Names cont
5. The + and - charges must balance out. Determine what charge needs to be on the metal to balance out the non metal. e.g. manganese must have a charge of 4+ to balance out 2 oxides with 2-
MnO2
Mn4+ O2- O2-

13. 6. Write the name of the compound with a Roman numeral
e.g. Manganese (IV) oxide
Example Cu3P MnO
Cu 2+ or 1+ Mn 2+ or 3+ or 4+
P3- so Cu1+ O2- so Mn2+
Copper (I) phosphide Manganese (II) oxide

14. Polyatomic ions 1. Identify each ion and its charge
e.g. ammonium carbonate NH4+ and CO32-
2. Determine the total charges needed to balance positive with negative and note the ratio of positive ions to negative ions
e.g = +2 and -2 so 2 ammonium ions and 1 carbonate ions

15. Polyatomic ions
OR use the cross over technique e.g. NH41+ CO Use subscripts and brackets to write the formula. Omit brackets if only one ion is needed e.g. (NH4)2CO3 Eg. Iron (III) hydroxide Ammonium sulphate Fe3+ OH- NH4+ SO42- Fe(OH)3 (NH4)2SO4

16. Handy chart

17. Writing names
1. Count the elements, if there is more than two then you have a polyatomic group. Figure out which grouping is the polyatomic.
e.g. Al2 (SO4)3 aluminum (not a multivalent) and sulphate (polyatomic)
2. Metal still goes first and doesn’t change.
3. Non metal goes second. If it’s a polyatomic the ending does not change to “ide” like an element does.
e.g. Aluminum sulphate
Ex. Fe3(PO4)2 NaOH
Iron (II) phosphate Sodium hydroxide