Ionic Formula Dissection Activity
Background
A chemical formula is a combination of symbols and numerical subscripts that
represent the composition of a compound. The symbol indicates which elements are present and
the numerical subscripts indicate how many atoms of each element make up the compound. The
subscripts can be predicted using ion charges. Ions are atoms that have acquired a charge. Ions
can be cations (having a positive charge) or anions (having a negative charge). Ions consisting
of more than one atom are called polyatomic ions.
It is important that all scientists use the same system for writing chemical formulas. This
helps to ensure clear and consistent transmission of information. Use the following rules when
writing chemical formulas:
Rule 1: Compounds are neutral, so the cation/anion charges must add up to 0.
(Na1+ Cl1-  NaCl  (1+) + (1-) = 0
Rule 2: Subscripts are used to balance ion charges so that the total charge on the
compound is 0.
Na1+ O2-  Na2O  2(1+) + (2-) = 0
Rule 3: If a subscript must be used to balance the charge of a polyatomic ion, the
polyatomic ion must be enclosed in parentheses and the subscript put on the outside of
the parentheses.
Al3+ NO31-  Al(NO3)3  (3) + 3(1-) = 0
Purpose
In this activity you will
 “Dissect formulas into cations, anions, and polyatomic ions
 Investigate the structure of a chemical formula
 Learn how to name chemical formulas
Procedure
Use your periodic table to help you ‘dissect’ each chemical formula in the data table into
cations, anions, and/or polyatomic ions. Write the symbol and charge of each cation or anion.
Then name it. Write the formula for each polyatomic ion. Then name it.
Prelab
1. What are the parts of a chemical formula and what do they tell you about the formula?
2. What is the difference between an ion and a polyatomic ion? Give an example of each.
3. Prove Rule #1 and #2 using CaF2. (State each rule and then prove each rule)
4. Count and identify the ions in this formula:
(NH4)2 CO3
5. Why are the parentheses necessary in question 4?
STOP: PROGRESS
CHECK!!!!
Data
A.
B.
C.
D.
E.
F.
NaCl
Na2CO3
NaOH
Na2SO4
Na3PO4
NaNO3
1.
NH4Br (NH4)2CrO4
(NH4)2S
(NH4)2SO3 (NH4)3PO3 NH4C2H3O2
2.
KCN
K2Cr2O7
K2O
K2C2O4
K3AsO4
KClO
CaSO4
Ca(ClO4)2
Ca(SCN)2
CaSe
Ca(HCO3)2
Ca(NO2)2
3.
4.
Part 1: Dissect each ionic formula!
Dissect each ionic formula above into the cation and the anion. Name each.
Ionic Compound Dissection
Number/
Letter
Formula
Cation/Positive
Polyatomic ion
Name
Anion/Negative
Polyatomic ion
Name
1A
NaCl
Na1+
Sodium
ion
Cl1-
Chloride
1B
1C
1D
1E
1F
2A
2B
2C
STOP: PROGRESS
CHECK!!!!
2D
2E
2F
3A
3B
3C
3D
3E
3F
4A
4B
STOP: PROGRESS
CHECK!!!!
4C
4D
4E
4F
Part 2: Name each chemical formula!
The cation name is the element name from the periodic table, or ammonium
(a positive polyatomic ion). The anion name ends in -ide or it comes from
the polyatomic ion reference sheet. Make no alterations to the polyatomic
ion name!
EXAMPLE 1: NaCl is the sodium ion and the anion chloride. The name of this formula is
sodium chloride.
EXAMPLE 2: (NH4)2 CO3. - NH41+ is a polyatomic ion called ammonium and CO32- is a
polyatomic ion called carbonate. The formula name is ammonium carbonate.
Ionic Compound Nomenclature
Number/
Letter
Formula
Formula Name
1A
NaCl
Sodium chloride
1B
1C
STOP: PROGRESS
CHECK!!!!
1D
1E
1F
2A
2B
2C
2D
2E
2F
3A
3B
3C
3D
3E
3F
STOP: PROGRESS
CHECK!!!!
4A
4B
4C
4D
4E
4F
Part 3: Write each chemical formula!
1
1. beryllium hypochlorite ______________________
2. barium bicarbonate________________________
3. ammonium dichromate_____________________
4. strontium sulfide__________________________
5. lithium selenide__________________________
6. aluminum carbonate_______________________
7. cesium oxide_____________________________
8. calcium bromide__________________________