Molecular Compounds
Writing Names and Formulas
Molecular Compounds
Molecular compounds are made of
molecules.
 They are made by joining nonmetal
atoms together into molecules.

Naming is Easier

A molecular compound’s name tells you
the number of atoms through the use of
prefixes.
Prefixes
1 mono 2 di 3 tri 4 tetra 5 penta
6 hexa 7 hepta 8 octa 9 nona 10 deca
Prefixes

The name will consist of two words.
Prefix name prefix name -ide

One exception is we don’t write
mono- if there is only one of the first
element.
Prefixes

The following double vowels cannot be
used when writing names:
 (oa)
 (oo)
Example

NO2

There is one nitrogen


mononitrogen
But, you cannot use mono- on the first
element, so drop the prefix.
 nitrogen
mononitrogen
Example

NO2

There are two oxygens

dioxygen
Example

NO2


dioxygen
You need the suffix -ide

diox ygen
ide
Example

NO2

nitrogen dioxide
Example

N2O

There are two nitrogens


dinitrogen
There is one oxygen

monooxygen
Example

N2O


monooxygen
You cannot run (oo) together, so

monoxygen
Example

N2O


monoxygen
You need the suffix -ide

monoxygen
ide
Example

N2O

dinitrogen monoxide
Problem

Name the following molecular
compounds.

Cl2O7

CBr4
dichlorine heptoxide
carbon tetrabromide
Problem

Name the following molecular
compounds.

CO2
carbon dioxide

BCl3
boron trichloride
Naming Molecular
Compounds
You will not need to criss-cross
oxidation numbers.
 Molecular compounds name tells you
the number of atoms through the use of
prefixes.

Example

diphosphorus pentoxide

The name implies there are 2
phosphorous atoms and 5 oxygens.
P2O5
Example

sulfur hexaflouride

The name implies there is 1 sulfur
atom and 6 fluorines.
SF6
Problem

Write the formulas for the following
molecules.
 tetraiodide nonoxide

nitrogen trioxide
I4O9
NO3
Problem

Write the formulas for the following
molecules.
 carbon tetrahydride

phosphorus trifluoride
CH4
PF3