1. Ionic Bonding and Nomenclature
Naming and Writing Formulas for Ionic Compounds

2. Naming and Writing Formulas for Ionic Compounds
Objectives 1. Name and write the symbols for common anions, cations, and polyatomic ions. 2. Determine the formula of an ionic compound between any two given ions. 3. Name ionic compounds, given their formulas. 4. Correctly use Roman numerals when naming compounds containing transition metals with more than one oxidation number. 5. Write formulas for ionic compounds, given their names.
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3. Naming and Writing Formulas for Ionic Compounds
In forming a chemical compound, an atom can gain, lose or share one or more valence electrons.
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4. Positive Ions
A cation is an atom or group of atoms with a positive charge. A cation has fewer electrons than a neutral atom of the element.
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5. Symbols of Ions for Cations
The metals in groups 1, 2 and 13 lose electrons when they form ions. Group 1 forms +1 ions. Group 2 forms +2 ions Group 13 forms +3 ions.
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6. Naming and Writing Symbols for Cations
Element
Symbol of Ion
Name of Ion
Calcium
Sodium
Aluminum
Ca2+
Calcium ion
Na+
Sodium ion
Al3+
Aluminum ion
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7. Metals with More than One Common Oxidation Number
The metals in groups 3-12 are called transition metals. They often have more than one common oxidation number (ionic charge).
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8. Metals with More than One Common Oxidation Number
Here are some of the more commonly used transition metals and their oxidation numbers. Notice that a Roman numeral is used to indicate the charge on the ion when naming the ions formed.
Fe2+ Iron(II) ion Fe3+ Iron(III) ion
Cu+ Copper(I) ion Cu2+ Copper(II) ion
Hg22+ Mercury(I) ion Hg2+ Mercury(II) ion
Pb2+ Lead(II) ion Pb4+ Lead(IV) ion
Sn2+ Tin(II) ion Sn4+ Tin(IV) ion
Cr2+ Chromium(II) ion Cr3+ Chromium(III) ion
Cr6+ Chromium(VI) ion
Mn2+ Manganese(II) ion Mn3+ Manganese(III) ion
Co2+ Cobalt(II) ion Co3+ Cobalt(III) ion
Ni2+ Nickel(II) ion Ni3+ Nickel(III) ion
Ag+ Silver ion
Zn2+ Zinc ion
Cd2+ Cadmium ion
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9. Negative Ions
An anion is an atom or group of atoms with a negative charge. An anion has more electrons than a neutral atom of the element. Group 17 forms -1 ions. Group 16 forms -2 ions. Group 15 forms -3 ions. The names of monatomic anions end in ide.
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10. Naming and Writing Formulas for Anions
Element
Symbol of Ion
Name of Ion
Chlorine
Nitrogen
Oxygen
Cl-
Chloride ion
N3-
Nitride ion
O2-
Oxide ion
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11. Number of Electrons Lost or Gained
You Try It
Complete the following table.
Symbol of Ion
Name of Ion
Number of Electrons Lost or Gained
Sulfide ion
Cu+
Barium ion
Al3+
Iron(III) ion
Li+
Phosphide ion
S2-
2 e- gained
Copper(I) ion
1 e- lost
Ba2+
2 e- lost
Aluminum ion
3 e- lost
Fe3+
3 e- lost
Lithium ion
1 e- lost
P3-
3 e- gained
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12. Predicting Formulas of Ionic Compounds
Ionic compounds are composed of charged particles called ions. They are electrically neutral. This means that the total positive charge is equal to the total negative charge. Binary ionic compounds usually consist of a metal, such as an alkali metal, bonded to a nonmetal, such as a halogen. Empirical formulas are used to represent ionic compounds. An empirical formula is the simplest ratio in which the atoms combine to form a compound.
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13. Predicting Formulas of Ionic Compounds
Examples: Write the formulas for the compounds formed between the following pairs of ions.
a. K+, Cl-
Mg2+, S2-
Na+, S2-
Al3+, S2-
Sn4+, O2-
KCl
MgS
Na2S
Al2S3
SnO2
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14. You Try It Sodium bromide Magnesium sulfide c. Copper(I) chloride
Write the formulas for the following binary ionic compounds. Hint: First determine the symbols for the ions involved. Always write the cation first. The first one has been done for you as an example.
Sodium bromide
Magnesium sulfide
c. Copper(I) chloride
d. Calcium bromide
e. Strontium fluoride
Na+, Br-
Mg2+, S2-
Cu+, Cl-
Ca2+, Br-
Sr2+, F-
NaBr
MgS
CuCl
CaBr2
SrF2
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15. j. Chromium(VI) nitride Na+, O2- Pb2+, Br- Zn2+, S2- Al3+, O2-
You Try It
Write the formulas for the following binary ionic compounds. Hint: First determine the symbols for the ions involved. Always write the cation first. The first one has been done for you as an example.
f. Sodium oxide
g. Lead(II) bromide
h. Zinc sulfide
i. Aluminum oxide
j. Chromium(VI) nitride
Na+, O2-
Pb2+, Br-
Zn2+, S2-
Al3+, O2-
Cr6+, N3-
Na2O
PbBr2
ZnS
Al2O3
CrN2
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16. Naming Binary Ionic Compounds
Binary ionic compounds are named by writing the name of the cation followed by the name of the anion (-ide ending).
a. Na2S
b. LiF
c. BaCl2
Sodium sulfide
Lithium fluoride
Barium chloride
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17. Roman Numerals
Sometimes it is necessary to use a Roman numeral when naming an ionic compound.
When do you use a Roman numeral when naming an ionic compound?
You use a Roman numeral when the metallic element forms more than one common ion. This is common of the transition metals.
CuCl is
CuCl2 is
Copper(I) Chloride
Copper(II) Chloride
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18. Roman Numerals
Never use a Roman numeral when the metallic element is from Group 1, Group 2, or for aluminum, cadmium, zinc or silver.
Circle the compounds below that would need a Roman numeral when naming them.
SnCl Fe2O BaCl LiF
MgS CaO SrF CoI3
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19. Roman Numerals
How do I determine the charge of the Roman numeral?
To determine the charge of the Roman numeral you have to first identify the ions making up the compound.
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20. Roman Numerals Examples. Iron(III) oxide Fe2O3 Cu2S Copper(I) sulfide
Ions
Chemical Formula
Name of Compound
Fe3+, O2-
Cu+, S2-
CoI2
Tin(IV) oxide
FeS
Cu3N
Fe2O3
Iron(III) oxide
Cu2S
Copper(I) sulfide
Co2+, I-
Cobalt(II) iodide
Sn4+, O2-
SnO2
Fe2+, S2-
Iron(II) sulfide
Cu+, N3-
Copper(I) nitride
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21. You Try It Li+, O2- Li2O SnS2 Sn4+, S2- Ba2+, N3- Ba3N2 Na+, F- NaF
Write formulas for the following compounds. Remember to determine the ions involved first.
Name of Compound
Ions
Formula of Compound
Lithium oxide
Tin(IV) sulfide
Barium nitride
Sodium fluoride
Li+, O2-
Li2O
SnS2
Sn4+, S2-
Ba2+, N3-
Ba3N2
Na+, F-
NaF
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22. You Try It Name the following compounds. a. CaS b. FeN c. K2O d. PbO
Calcium sulfide
Iron(III) nitride
Potassium oxide
Lead(II) oxide
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23. Naming and Writing Formulas for Ternary Ionic Compounds
Ternary ionic compounds contain more than two elements. They usually contain one or more polyatomic ions.
Common Polyatomic Ions
1- Charge
2- Charge
3- Charge
Perchlorate
ClO4-
Carbonate
CO32-
Phosphate
PO43-
Chlorate
ClO3-
Sulfate
SO42-
Phosphite
PO33-
Chlorite
ClO2-
Sulfite
SO32-
Hypochlorite
ClO-
Chromate
CrO42
1+ Charge
Nitrate
NO3-
Dichromate
Cr2O72-
Ammonium
NH4+
Nitrite
NO2-
Oxalate
C2O42-
Iodate
IO3-
Silicate
SiO32-
Bromate
BrO3-
Hydrogen Phosphate
HPO42-
Permanganate
MnO4-
Hydroxide
OH-
Cyanide
CN-
Acetate
C2H3O2-
Dihydrogen phosphate
H2PO4-
Hydrogen Sulfite (bisulfate)
HSO3-
Hydrogen sulfate (bisulfate)
HSO4-
Hydrogen carbonate (bicarbonate)
HCO3-
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24. Writing Formulas for Ternary Ionic Compounds
Writing the formulas for ternary ionic compounds is just like writing the formula for binary ionic compounds. You write the symbol and charge of the ions involved and then balance the charges.
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25. Writing Formulas for Ternary Ionic Compounds
Examples:
a. K+, NO3-
b. Ba2+, PO43-
KNO3
Ba3(PO4)2
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26. You Try It
1. Write the formulas for the following ternary ionic compounds, given the ions involved.
a. Ca2+, SO42-
b. K+, PO43-
c. NH4+, N3-
d. Al3+, SO42-
CaSO4
K3PO4
(NH4)3N
Al2(SO4)3
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27. You Try It
2. Write the formulas for the following ternary ionic compounds given their names.
Lithium hypochlorite
Sodium sulfite
Calcium acetate
Barium phosphate
Copper(II) nitrite
Li+, ClO-
Na+, SO32-
Ca2+, C2H3O2-
Ba2+, PO43-
Cu2+, NO2-
LiClO
Na2SO3
Ca(C2H3O2)2
Ba3(PO4)2
Cu(NO2)2
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28. You Try It
3. To name a compound, write the name of the cation followed by the name of the anion.
a. Ca(NO3)2
b. K2SO4
c. PbSO3
d. NaC2H3O2
e. (NH4)2S
Calcium nitrate
Potassium sulfate
Lead(II) sulfite
Sodium Acetate
Ammonium sulfide
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