1. Chapter 9 Chemical Names and Formulas
9.1 Naming Ions
9.2 Naming and Writing Formulas for Ionic
Compounds
9.3 Naming and Writing Formulas for
Molecular Compounds
9.4 Naming and Writing Formulas for Acids and
Bases
9.5 The Laws Governing How Compounds Form
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2. Binary Molecular Compounds
What guidelines are used to write the name and formula of a binary molecular compound?
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3. Binary Molecular Compounds
Recall that binary ionic compounds are composed of the ions of two elements, a metal and a nonmetal.
Binary molecular compounds are also composed of two elements, but both elements are nonmetals and are not ions.
Binary molecular compounds are composed of molecules, not ions, so ionic charges cannot be used to write formulas or to name them.
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4. Binary Molecular Compounds
When two nonmetallic elements combine, they often do so in more than one way.
For example, the elements carbon and oxygen combine to form two gaseous compounds, CO and CO2.
It might seem satisfactory to call both of these compounds carbon oxide.
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5. Binary Molecular Compounds
However, the two carbon oxides, CO and CO2, are very different compounds.
You exhale CO2 as a product of your body chemistry, and it is normally present in the air you breathe.
CO is a poisonous gas that interferes with your blood’s ability to carry oxygen to body cells.
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6. Binary Molecular Compounds
When you exhale underwater, bubbles containing CO2 rise to the surface of the water.
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7. Binary Molecular Compounds
Naming Binary Molecular Compounds
Prefixes Used in Naming Binary Molecular Compounds
Prefix
Number
mono- 1
di- 2
tri- 3
tetra- 4
penta- 5
hexa- 6
hepta- 7
octa- 8
nona- 9
deca- 10
Prefixes in the names of binary molecular compounds help distinguish compounds containing different numbers of atoms, such as CO and CO2.
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8. Binary Molecular Compounds
Naming Binary Molecular Compounds
Prefixes in the names of binary molecular compounds tell how many atoms of an element are present in each molecule of the compound.
The prefix mono- would be used for the single oxygen atom in CO.
The prefix di- would be used for the two oxygen atoms in CO2.
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9. Binary Molecular Compounds
Naming Binary Molecular Compounds
Use the prefixes listed in the table along with the guidelines on the next slides to name a binary molecular compound.
Before you apply these steps, you must confirm that the compound is a binary molecular compound.
Note: These compounds are made of two anions (2 nonmetals or 1 nonmetal & 1 polyatomic ion)
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10. Binary Molecular Compounds
To name a binary molecular compound, use the following guidelines.
Write the names of the elements in the order listed in the formula.
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11. Binary Molecular Compounds
To name a binary molecular compound, use the following guidelines.
Write the names of the elements in the order listed in the formula.
Use prefixes appropriately to indicate the number of each kind of atom.
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12. Binary Molecular Compounds
To name a binary molecular compound, use the following guidelines.
Write the names of the elements in the order listed in the formula.
Use prefixes appropriately to indicate the number of each kind of atom.
If just one atom of the first element is in the formula, omit the prefix mono- for that element. Also, the vowel at the end of a prefix is sometimes dropped when the name of the element begins with a vowel.
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13. Binary Molecular Compounds
To name a binary molecular compound, use the following guidelines.
Write the names of the elements in the order listed in the formula.
Use prefixes appropriately to indicate the number of each kind of atom present in formula.
If just one atom of the first element is in the formula, omit the prefix mono- for that element. Also, the vowel at the end of a prefix is sometimes dropped when the name of the element begins with a vowel.
End the name of the second element with the suffix -ide. (unless its polyatomic)
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14. Binary Molecular Compounds
Naming Binary Molecular Compounds
Following these guidelines,
CO is named carbon monoxide
CO2 is named carbon dioxide.
Cl2O8 consists of two chlorine atoms and eight oxygen atoms.
The name is therefore dichlorine octoxide.
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15. Binary Molecular Compounds
Writing Formulas for Binary Molecular Compounds
To write the formula of a binary molecular compound, first use the prefixes in the name to tell you the subscript of each element in the formula. Then, write the correct symbols for the two elements with the appropriate subscripts.
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16. Binary Molecular Compounds
Writing Formulas for Binary Molecular Compounds
An interesting example is tetraphosphorus trisulfide, which is used in some matches.
The name tetraphosphorus trisulfide has the prefixes tetra- and tri-, so the subscripts of phosphorus and sulfur must be 4 and 3, respectively.
Thus, the formula for tetraphosphorus trisulfide is P4S3.
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17. Naming Molecular Compounds
3. S2F6 -
4. P4O10 -
5. N2O4 -

18. 1. CO -carbon monoxide
2. CO2--carbon dioxide
3. S2F6 - disulfur hexafluoride
4. P4O10 -tetraphosphorus decoxide
5. N2O4 -dinitrogen tetroxide

19. Naming Molecular Compounds
6. NCl3 -
7. PBr5 -
8. SiS2 -
9. N2F4 -
10. SeBr2 -

20. 6. NCl3 - nitrogen trichloride
7. PBr5 - phosphorus pentabromide
8. SiS2 - silicon disulfide
9. N2F4 - dinitrogen tetrafluoride
10. SeBr2 -selenium dibromide

21. Covalent Compound Practice
Name the following:
SO2 ___________________________
N2O ___________________________
NO2 ___________________________
CCl4 ___________________________
Cl2O7 ___________________________

22. Covalent Compound Practice
SO2 Sulfur Dioxide
N2O -Dinitrogen Monoxide
NO2 - Nitrogen Dioxide
CCl4 -Carbon Tetrachloride
Cl2O7-Dichlorine Heptaoxide

23. Covalent Compound Practice
Name the following:
PCl3 ___________________________
SF6___________________________
Si3N4___________________________
N(BrO3)5___________________________
H2O___________________________

24. Covalent Compound Practice
PCl3 - Phosphorus Trichloride
SF6 -Sulfur Hexaflouride
Si3N4 - Trisilicon Tetranitride
N(BrO3)5 - Nitrogen Pentabromate
H2O-Water  - can use common name

25. Covalent Compound Practice
Name compound or write the formula:
Phosphorus Trioxide- _____________
N2C5 - ___________________________
TeI9- ____________________________
Carbon Monoxide_________________ :

26. Covalent Compound Practice
Phosphorus Trioxide - PO3
N2C5-Dinitrogen Pentacarbide
TeI9 -Tellurium Noniodide
Carbon Monoxide -CO

27. Covalent Compound Practice
Selenium Heptaflouride –
P4O10-
Arsenic Hexabromide –
SiCl2 –

28. Covalent Compound Practice
Selenium Heptaflouride – SeF7
P4O10- Tetraphosphorous Decoxide
Arsenic Hexabromide - AsBr6
SiCl2 - Silicon Dichloride

29. What are binary molecular compounds composed of?
Binary molecular compounds are composed of two elements, which are nonmetals and are not ions.
How is their composition different from binary ionic compounds?
Binary ionic compounds are composed of the ions of two elements, a metal and a nonmetal.
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30. Key Concepts
To name a binary molecular compound, write the names of the elements in the order listed in the formula. Use prefixes to indicate the number of each atom. End the name of the second element with -ide.
To write the formula of a binary molecular compound, use the prefixes to determine the subscript of each element. Write the symbols for the elements with the subscripts.
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31. BIG IDEA
Ionic and molecular compounds differ in composition—ions form ionic compounds, and molecules form molecular compounds.
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32. END OF 9.3
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