Chapter 9.3
Naming and Writing
Formulas for Molecular
Compounds
Naming Binary Molecular
Compounds

In molecular compounds, both elements are
nonmetals.
 The elements involved are not ions…ionic
naming rules do not apply.
 Prefixes are used to distinguish compounds
containing different amounts of the same two
elements.
 The prefix in the name of a binary molecular
compound tells how many atoms of each
element are present in each molecule of the
compound.
 Prefixes
used are in table 9.4.
 CO is carbon monoxide.
 CO2 is carbon dioxide.
 N2O is dinitrogen oxide.
 The names of all binary molecular
compounds end in –ide.
 The vowel at the end of the prefix is often
dropped.
 Carbon monoxide, not carbon monooxide.
Naming Guidelines
 Confirm
compound is binary molecular.
 Name elements in order listed in formula.
 Use prefixes to indicate the number of
each kind of atom.
 Omit mono- when the formula contains
only one atom of the first element in the
name.
 The suffix of the second element is –ide.
 Practice…
 SF6
 sulfur
hexaflouride
 Cl2O8
 dichlorine
octoxide
Writing Formulas for Binary
Molecular Compounds
 Simple.
Use prefixes in the name to tell
you the subscript of each element in the
formula.
 Then write the correct symbols of the two
elements with the appropriate subscripts.
 Practice…silicon carbide
 SiC
 dinitrogen tetroxide
 N2O4