1. Naming and Writing Formulas For Covalent (Molecular) Compounds Acids

2. Naming Binary Molecular Compounds
The naming of molecular compounds is based on the use of prefixes (CO is carbon monoxide, CO2 is carbon dioxide, P4O10 is tetraphosphorus decoxide).
The less electronegative element is given first. It is given a prefix only if it contributes more than one atom to a molecule.
The second element is named by (a) prefix giving number of atoms contributed (b) the root of the name of the second element, and (c) the ending –ide.

3. Numerical Prefixes Number 1 2 3 4 5 6 7 8 9 10 Prefix mono- di- tri-
tetra-
penta-
hexa-
hepta-
octa-
nona-
deca-

4. As2O5 diarsenic pentoxide
The prefix system is illustrated below.
As2O5
Prefix indicating number of
atoms contributed by second
element.
Prefix needed if first
element contributes
more than one atom + +
Root name of second element
+ ide.
Name of
first element
diarsenic
pentoxide

5. Acids
An acid can be viewed as a molecule with one or more H+ ions attached to an anion.
The rules for naming acids depend on whether the anion contains oxygen.
If the anion does not contain oxygen, the acid is named with the prefix hydro- and the suffix –ic.
For example, when gaseous HCl is dissolved in water, it forms hydrochloric acid.

6. When the anion contains oxygen, the acidic name is formed from the root name of the anion with a suffix of –ic or –ous, depending on the name of the anion.
If the anion name ends in –ate, the suffix –ic is added to the root name.
For example, H2SO4 contains the sulfate anion (SO42-) and is called sulfuric acid.
If the anion has an –ite ending, the –ite is replaced by –ous.
For example, H2SO3, which contains sulfite (SO32-), is named sulfurous acid.

7. Flowchart for Naming Acids.

8. Example: name the following acids.
HI(g) dissolved in water
The anion does not contain oxygen so the prefix hydro- and the suffix –ic is added.
Hydroiodic acid
HClO4
The anion contains oxygen and is called perchlorate so the suffix –ic is added to the name.
Perchloric acid

9. Acid Formulas
When writing formulas for acids the charge on the anion must be taken into account.
For example, if the charge on the anion is -1 then one hydrogen ion (H+) is added to balance charge.
If the charge on the anion is -2 then two hydrogen ions are added to balance charge.