1. Ionic Compound Formulas

2. Ions Cation: A positive ion Mg2+, NH4+ Anion: A negative ion
Cl-, SO42-

3. Oxidation Number
the total number of electrons that an atom either gains or loses in order to form a chemical bond with another atom.

4. Predicting Ionic Charges
Group 1:
Lose 1 electron to form 1+ ions H+
Li+
Na+ K+

5. Predicting Ionic Charges
Group 2:
Loses 2 electrons to form 2+ ions
Be2+
Mg2+
Ca2+
Sr2+
Ba2+

6. Predicting Ionic Charges
Loses 3
electrons to form
3+ ions
Group 13:
B3+
Al3+
Ga3+

7. Predicting Ionic Charges
Lose 4
electrons or gain
4 electrons?
Group 14:
Neither! Group 13 elements rarely form ions*** few exceptions

8. Predicting Ionic Charges
Nitride
Gains 3
electrons to form
3- ions
Group 15:
Phosphide
P3-
As3-
Arsenide

9. Predicting Ionic Charges
Oxide
Gains 2
electrons to form
2- ions
Group 16:
S2-
Sulfide
Se2-
Selenide

10. Predicting Ionic Charges
Group 17:
Gains 1
electron to form
1- ions
F1-
Fluoride
Cl1-
Chloride
Br1-
Bromide
I1-
Iodide

11. Predicting Ionic Charges
Group 18:
Stable Noble gases do not form ions!

12. Predicting Ionic Charges
Many transition elements
have more than one possible oxidation state.
Groups :
Iron(II) = Fe2+
Iron(III) = Fe3+

13. Predicting Ionic Charges
Some transition elements
have only one possible oxidation state.
Groups :
Zinc = Zn2+
Silver = Ag+

14. Elements that form Ions
Metals usually form cations while Nonmetals usually form anions

15. Writing Ionic Compound Formulas
Example: Barium nitrate
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
Ba2+
( )
NO3- 2
Not balanced!

16. Writing Ionic Compound Formulas
Example: Ammonium sulfate
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
( )
NH4+
SO42- 2
Not balanced!

17. Writing Ionic Compound Formulas
Example: Iron(III) chloride
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
Fe3+
Cl- 3
Not balanced!

18. Writing Ionic Compound Formulas
Example: Aluminum sulfide
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
Al3+
S2- 2 3
Not balanced!

19. Writing Ionic Compound Formulas
Example: Magnesium carbonate
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
Mg2+
CO32-
They are balanced!

20. Writing Ionic Compound Formulas
Example: Zinc hydroxide
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
( )
Zn2+
OH- 2
Not balanced!

21. Writing Ionic Compound Formulas
Example: Aluminum phosphate
1. Write the formulas for the cation and anion, including CHARGES!
2. Check to see if charges are balanced.
Al3+
PO43-
They ARE balanced!

22. Example: Aluminum Chloride
Criss-Cross Rule
Example: Aluminum Chloride
Aluminum Chloride
Step 1:
write out name with space
Al Cl 3+ 1-
Step 2:
write symbols & charge of elements
Al Cl
Step 3: 1 3
criss-cross charges as subsrcipts
Step 4: AlCl 3
combine as formula unit
(“1” is never shown)

23. Example: Aluminum Chloride
Criss-Cross Rule
Example: Aluminum Chloride
Step 1: Aluminum Chloride
Step 2: Al3+ Cl1-
Step 3: Al Cl 1 3
Step 4: AlCl 3

24. Example: Aluminum Oxide
Criss-Cross Rule
Example: Aluminum Oxide
Step 1: Aluminum Oxide
Step 2: Al3+ O2-
Step 3: Al O 2 3
Step 4: Al2O3

25. Example: Magnesium Oxide
Criss-Cross Rule
Example: Magnesium Oxide
Step 1: Magnesium Oxide
Step 2: Mg2+ O2-
Step 3: Mg O 2 2
Step 4: Mg2O2
Step 5: MgO

26. Naming Ionic Compounds
Cation first, then anion
Monatomic cation = name of the element
Ca2+ = calcium ion
Monatomic anion = root + -ide
Cl- = chloride
CaCl2 = calcium chloride

27. Multiple Charge Cations
Ion Stock System Traditional System
Fe 3+ iron (III) ferric
Fe 2+ iron (II) ferrous
Cu 2+ copper (II) cupric
Cu 1+ copper (I) cuprous
Co 3+ cobalt (III) cobaltic
Co 2+ cobalt (II) cobaltous
Sn 4+ tin (IV) stannic
Sn 2+ tin (II) stannous
Pb 4+ lead (IV) plumbic
Pb 2+ lead (II) plumbous
Hg 2+ mercury (II) mercuric
Hg2 2+ mercury (I) mercurous
*Mercury (I) ions are always bound together in pairs to form Hg2 2+
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 90

28. Naming Ionic Compounds
Metals with multiple oxidation states
some metal forms more than one cation
use Roman numeral in name
PbCl2
Pb2+ is cation
PbCl2 = lead(II) chloride

29. Naming Binary Compounds
Formula Name
barium oxide
BaO ____________________
________________ sodium bromide
MgI2 ____________________
KCl ____________________
________________ strontium fluoride
________________ cesium fluoride
NaBr
magnesium iodide
potassium chloride
SrF2
CsF