# How do you name acids?

Jan 22, 2016

It depends on what acid you are talking about.

The two common types of acids that you might mean from general and inorganic chemistry are:

• hydrohalogenic acids
• oxoacids

As some examples...

HYDROHALOGENIC ACIDS

As the name suggests, it has hydrogen and a halogen. You would name $\text{HCl}$ by noting that it has a chloride anion and a hydrogen cation (aka proton).

With hydrohalogenic acids, you can tell that you add an ic at the end of the prefix for chlorine without a terminating vowel ("chlor" + "ic", but not "chloro" + "ic"). Then, just add "acid" at the end.

Thus, it is called hydrochloric acid .

Similarly, $\text{HBr}$ and $\text{HI}$ have halogenic components that are given names constructed like so:

• "hydro" + "brom" + "ic", not "bromo" + "ic"
• "hydro" + "iod" + "ic", not "iodo" + "ic"

Then add "acid" at the end.

OXOACIDS/OXYACIDS

As the name suggests, it has oxygen. In addition, it has a suitable central atom. The prefix of the acid name is based off of the central atom name.

Based on the number of oxygens relative to the maximum possible, the suffix changes, and then you add "acid" at the end. However, note that it is based specifically off of the particular polyatomic ion names, not purely the number of oxygens.

$\left(3 -\right)$ ion example:

• Phosphate is ${\text{PO}}_{4}^{3 -}$, so the triprotic acid would be ${\text{H"_3"PO}}_{4}$, which is called Phosphoric acid (not phosphic acid).
• Phosphite is ${\text{PO}}_{3}^{3 -}$, so the triprotic acid would be ${\text{H"_3"PO}}_{3}$, which is called Phosphorous acid (not phosphous acid).

$\left(2 -\right)$ ion example:

• Sulfate is ${\text{SO}}_{4}^{2 -}$, so the diprotic acid would be ${\text{H"_2"SO}}_{4}$, which is called Sulfuric acid (not sulfic acid).
• Sulfite is ${\text{SO}}_{3}^{2 -}$, so the diprotic acid would be ${\text{H"_2"SO}}_{3}$, which is called Sulfurous acid (not sulfous acid).

On the other hand... nitrate only has three oxygens, not four.

$\left(1 -\right)$ ion example:

• Nitrate is ${\text{NO}}_{3}^{-}$, so the monoprotic acid would be ${\text{HNO}}_{3}$, which is called Nitric acid.
• Nitrite is ${\text{NO}}_{2}^{-}$, so the monoprotic acid would be ${\text{HNO}}_{2}$, which is called Nitrous acid.

Some halogenic oxoacids use additional rules. Append "Per" for the highest number of oxygens while using "ic", but append "hypo" for the lowest number of oxygens while using "ous".

Example using a chlorine oxo acid:

• Perchlorate is ${\text{ClO}}_{4}^{-}$, so ${\text{HClO}}_{4}$ is Perchloric acid.
• Chlorate is ${\text{ClO}}_{3}^{-}$, so ${\text{HClO}}_{3}$ is Chloric acid.
• Chlorite is ${\text{ClO}}_{2}^{-}$, so ${\text{HClO}}_{2}$ is Chlorous acid.
• Hypochlorite is ${\text{ClO}}^{-}$, so $\text{HClO}$ is hypochlorous acid.

Or, the bromine oxo acid:

• Perbromate is ${\text{BrO}}_{4}^{-}$, so ${\text{HBrO}}_{4}$ is Perbromic acid.
• Bromate is ${\text{BrO}}_{3}^{-}$, so ${\text{HBrO}}_{3}$ is Bromic acid.
• Bromite is ${\text{BrO}}_{2}^{-}$, so ${\text{HBrO}}_{2}$ is Bromous acid.
• Hypobromite is ${\text{BrO}}^{-}$, so $\text{HBrO}$ is hypobromous acid.