1. Naming and Writing IONIC Chemical Formulas
Chem Lab Methods
Naming and Writing IONIC Chemical Formulas

2. Chemical Symbols

3. Chemical Formulas: Writing
Use the chemical symbol for each element
Usually, the element abbreviations come from the word
(He for Helium or Ti for Titanium)
Some elements have just one letter, such as H for Hydrogen or N for Nitrogen

4. Chemical Formulas: Writing
Most elements have two letters
Always capitalize the first letter and use lower case on the second one.
Example: Cobalt is Co
If you used two capitals (CO), it would be mistaken for Carbon Monoxide which has one Carbon (C) and one Oxygen (O)

5. Chemical Formulas: Subscripts
The subscript number specifies how many atoms of that element you have
N2 is a nitrogen molecule with two atoms
C2H4 has two carbons and four hydrogens
CO2 contains one carbon and two oxygens
If no number is listed, it means there is only one

6. Example
C2H3Cl
what elements and how many of each?

7. Example
C2H3Cl
what elements and how many of each?

8. Example
H2SiCl2
what elements and how many of each?

9. Example
H2SiCl2
what elements and how many of each?

10. Chemical Formulas: Coefficients (numbers in front)
what elements and how many of each?

11. Chemical Formulas: Coefficients (numbers in front)
CH4 => methane
what elements and how many of each?

12. Chemical Formulas: Coefficients (numbers in front)
When there are large numbers in front, that tells you how many molecules there are.
For example 3CH4 =

13. Chemical Formulas: Coefficients (numbers in front)
When there are large numbers in front, that tells you how many molecules there are.
For example 3CH4 = 3 methane molecules
12NaOH = ?

14. Chemical Formulas: Coefficients (numbers in front)
When there are large numbers in front, that tells you how many molecules there are.
For example 3CH4 = 3 methane molecules
12NaOH =
12 different
Sodium Hydroxide units

15. Practice
Counting Atoms

16. Definitions Nomenclature: Choosing of names for things
Naming procedure
Ionic Compound:
Atoms held together by ionic bonds
Binary Compound:
Chemical compound made of atoms from two different elements

17. Naming: Binary Ionic Compounds
Metal element name first
Then the non-metal element name, but the ending is changed to -ide
Example: CaCl2 would be called calcium chloride
Example: Ag2O would be called…
silver oxide

18. Practice
Naming Binary Compounds

19. Ionic Formulas: Developing
Example: Compound name - Magnesium chloride …What is the formula?

20. Ionic Formulas: Developing
Magnesium Chloride =
What charge ion would each atom form?
Mg+2
Cl-1
How many of each to make a neutral compound?

21. Ionic Formulas: Developing
Magnesium Chloride
Magnesium= Mg+2 => +2 charge
Chlorine = Cl-1 => -1 charge
The charges must balance (final compound is neutral)
Need TWO Cl-1 ions to balance one Mg+2 ion
(2 x -1) = (1 x +2) = 2 each
MgCl2

22. Ionic Formulas: Developing
Magnesium Chloride = 1 Mg Cl-1 => MgCl2
Mg+2
Cl-1

23. Ionic Formulas: Developing
Example: Compound name Lithium sulfide …What is the formula?

24. Ionic Formulas: Developing
Lithium Sulfide=
What charge ion would each atom form?
Li+1
S-2
How many of each to make a neutral compound?

25. Ionic Formulas: Developing
Lithium Sulfide
Lithium= Li+1
Sulfur = S-2
The charges must balance (final compound is neutral)
Need TWO Li+1 ions to balance one S-2 ion
(2 x +1) = (1 x -2) = two each
Li2 S

26. Ionic Formulas: Developing
Lithium sulfide = 2 Li S-2 => Li2S
Li+1
S-2

27. Ionic Formulas: Developing
Example: Compound name Boron oxide …What is the formula?

28. Ionic Formulas: Developing
Boron Oxide=
What charge ion would each atom form?
B+3
O-2
How many of each to make a neutral compound?

29. Ionic Formulas: Developing
Boron oxide
Boron= B+3
Oxygen = O-2
The charges must balance (final compound is neutral)
Need SIX cations (B+3) and SIX anions (O-2)
(2 x +3) = (3 x -2) = six each
B2O3
2 X 3 = 6

30. Ionic Formulas: Developing
Boron Oxide = 2 B O-2 => B3O2
B+3
O-2

31. Ionic Formulas: Developing
SUMMARY of approach:
Determine what charge ion would form from each element
Decide how many of each charge are needed to have a balanced (neutral) formula
Write formula
Subscripts state how many of each ion are needed

32. Ionic Formulas: KEY POINT
Ionic compound formula describes:
One “unit” of the chemical compound
Thus, it is called a “formula unit”
Important definition
Example: 3 CaCl2
Three “formula units” of calcium chloride

33. Practice
Writing (Balanced) Chemical Formulas

34. Ionic Formulas: Continued….
Two more details:
Complex ions: contain more than one element
Transition metals: ionic charges can vary

35. Ionic Formulas: Complex Ions
Examples:
Acetate is (C2H3O2)-1
Whole group has -1 ionic charge
Carbonate is (CO3 )-2
Whole group has -2 ionic charge
The ENTIRE group has one ionic charge
Acts like a single-atom ion of the same charge
List of common complex ions on the back of your periodic table

36. Ionic Formulas: Complex Ions
All but ONE of the common complex ions are negative
Phosphate is (PO3)-3
Whole group has -3 ionic charge
Chlorate is (ClO3 )-1
Whole group has -1 ionic charge
THE positive complex ion (worth memorizing) is:
Ammonium (NH4)+1

37. Ionic Formulas: Complex Ions
Magnesium Carbonate
Magnesium= Mg+2
Carbonate = (CO3)-2
The charges must balance (final compound is neutral)
Mg (CO3)

38. Ionic Formulas: Complex Ions
Magnesium Phosphate
Magnesium= Mg+2
Phosphate = (PO4)-3
The charges must balance (final compound is neutral)
Need SIX cations (Mg+2) and SIX anions (PO4 -3)
(3 x +2) = (2 x -3) = six each
Mg3 (PO4)2
2 X 3 = 6

39. Ionic Formulas: Transition Metals
Ionic charge can vary
How do you know?
Listed on Periodic Table
“Clue” in name

40. Examples of naming for metals with multiple charges
Element
Cation
Name
Pronounced
Copper
Cu+
Cu2+
Iron
Fe2+
Fe3+
Lead
Pb2+
Pb4+
Tin
Sn2+
Sn4+

41. Examples of naming for metals with multiple charges
Element
Cation
Name
Pronounced
Copper
Cu+
Copper (I)
copper one
Cu2+
Iron
Fe2+
Fe3+
Lead
Pb2+
Pb4+
Tin
Sn2+
Sn4+

42. Examples of naming for metals with multiple charges
Element
Cation
Name
Pronounced
Copper
Cu+
Copper (I)
copper one
Cu2+
Copper (II)
copper two
Iron
Fe2+
Fe3+
Lead
Pb2+
Pb4+
Tin
Sn2+
Sn4+

43. Examples of naming for metals with multiple charges
Element
Cation
Name
Pronounced
Copper
Cu+
Copper (I)
copper one
Cu2+
Copper (II)
copper two
Iron
Fe2+
Iron (II)
iron two
Fe3+
Iron (III)
iron three
Lead
Pb2+
Pb4+
Tin
Sn2+
Sn4+

44. Examples of naming for metals with multiple charges
Element
Cation
Name
Pronounced
Copper
Cu+
Copper (I)
copper one
Cu2+
Copper (II)
copper two
Iron
Fe2+
Iron (II)
iron two
Fe3+
Iron (III)
iron three
Lead
Pb2+
Lead (II)
lead two
Pb4+
Lead (IV)
lead four
Tin
Sn2+
Tin (II)
tin two
Sn4+
Tin (IV)
tin four

45. Ionic Formulas: Transition Metal Example
Write the chemical formula for Iron (II) Oxide
Step One: Determine the charges
Iron (II) = Fe2+ and Oxide = O2-
Step Two: See how to balance the charges
Step Three: Find the combination that balances
Iron (II) Oxide = FeO

46. Ionic Formulas: Transition Metal Example
Write the chemical formula for Lead (II) Nitride
Step One: Determine the charges
Lead (II) = Pb+2 and Nitride = N-3
Step Two: See how to balance the charges
Step Three: Find the combination that balances
Lead (II) Nitride = Pb3 N2

47. How do you know if you use Roman numerals?
Do not use Roman Numerals for groups 1 or 2 as they are always (+1) and (+2) accordingly.
K = and Ca = +2 +1 +2

48. How do you know if you use Roman numerals?
Do not use Roman numerals for transition metals that always form the same charge ion.
Ag = +1 and Zn = +2 and Cd = +2

49. Practice
Ionic Compound Formula Writing (all types)