1. Chapter 9: Chemical Names and Formulas
Naming and writing formulas for molecular compounds

2. Determine the name and/or formula of a molecular compound.
Learning Target
You will:
Determine the name and/or formula of a molecular compound.

3. You will determine the name and/or formula of a molecular compound.
Let’s think …
How many events are in a triathlon?
How do you know that?
Prefixes are used in naming molecular compounds.
They help distinguish compounds containing different numbers of atoms.
You will determine the name and/or formula of a molecular compound.

4. You will determine the name and/or formula of a molecular compound.
Molecular Compounds
Recall that ionic compounds are composed of ions of elements - metals and nonmetals.
Molecular compounds are also composed of elements but both are nonmetals, not ions.
Composed of molecules, not ions, so charges aren’t used for the formula or name.
You will determine the name and/or formula of a molecular compound.

5. You will determine the name and/or formula of a molecular compound.
Molecular Compounds
Two nonmetals can combine in more than one way.
Prefixes help distinguish compounds containing different numbers of atoms of nonmetals.
Prefixes tell how many atoms of an element are present in each molecule of the compound.
You will determine the name and/or formula of a molecular compound.

6. You will determine the name and/or formula of a molecular compound.
Thinking time …
How does a triathlon differ from a pentathlon?
How does phosphorus trifluoride differ from phosphorus pentafluoride?
A triathlon is composed of 3 sports, while a pentathlon is composed of 5.
Phosphorus trifluoride is a binary molecular compound that has 1 phosphorus and 3 fluoride atoms, while phosphorus pentafluoride contains 1 phosphorus and 5 fluoride atoms.
You will determine the name and/or formula of a molecular compound.

7. You will determine the name and/or formula of a molecular compound.
Naming and Writing
Naming Formulas:
First element listed in the formula is named first, using the full element name.
Second element listed in the formula is named as an anion.
Prefixes are used to tell the number of atoms present. (from the subscripts)
1st element gets a prefix EXCEPT when there is one atom.
2nd element ALWAYS get a prefix.
Writing Formulas:
Write the element symbols in order listed in the formula.
Change the prefixes to subscripts.
DON’T assign charges OR cross down
Remember if there is no prefix it means the subscript equals one
You will determine the name and/or formula of a molecular compound.

8. Examples CCl4 arsenic trifluoride NO2 dioxygen difluoride IF5
Write the name or formula for the following compounds:
CCl4
arsenic trifluoride
NO2
dioxygen difluoride
IF5
nitrogen monoxide
BF3
Silicon dioxide
Answers:
Carbon tetrachloride
AsF3
Nitrogen dioxide
O2F2
Iodine pentafluoride NO
Boron trifluoride
SiO2
You will determine the name and/or formula of a molecular compound.

9. Write the name or formula for the following compounds:
Try on your own
Write the name or formula for the following compounds:
xenon hexafluoride
N2O5
Diphosphorus pentoxide
I2O7
Chlorine trifluoride
CO2
Nitrogen monoxide
CF4
Answers:
XeF6
Dinitrogen pentoxide
P2O5
Diiodine heptoxide
ClF3
Carbon dioxide NO
Carbon tetrafluoride

10. Determine the name and/or formula of a molecular compound.
Summarize
You will:
Determine the name and/or formula of a molecular compound.