Ternary Acid
Definition and meaning of Ternary Acid in chemistry.
A ternary acid is a specific type of acid made of hydrogen, oxygen, and a third nonmetal element. These reactive compounds are also commonly known as oxyacids. They form when an acidic hydrogen atom attaches to an oxygen-rich polyatomic ion.
In more detail
When you mix these acids into water, they break apart to release positive hydrogen ions. These free floating hydrogen ions are exactly what make the liquid behave like an acid. The overall chemical strength of the acid depends on its central nonmetal atom and its oxygen atoms.
Having more oxygen atoms will always make the acid much stronger. The extra oxygen atoms pull negative electrons away from the hydrogen bond. This strong pulling action makes it much easier for the hydrogen to snap off and float away into the water.
Students often struggle to name these acids because the rules feel very strict. The name of the acid depends entirely on the name of its negative polyatomic ion. If the ion name ends with the suffix "ate", the acid name will end with "ic".
If the ion name ends with "ite", the acid name will end with "ous". A very common mistake is adding the prefix "hydro" to the front of the name. You never use the prefix "hydro" when naming any ternary acid. That specific prefix is only allowed for simple binary acids that do not contain any oxygen.
Key facts
| Composition | Contains hydrogen, oxygen, and a central nonmetal element. |
|---|---|
| Alternative name | Often referred to as an oxyacid or oxoacid. |
| Naming rule for 'ate' ions | Acids made from an 'ate' ion end in 'ic'. |
| Naming rule for 'ite' ions | Acids made from an 'ite' ion end in 'ous'. |
| Acid strength | Increases when more oxygen atoms are added to the molecule. |
Sulfuric acid is a very famous and industrially important ternary acid. Its chemical formula is written as H2SO4. You can see it contains hydrogen, sulfur, and oxygen atoms. The central sulfur atom is surrounded by four oxygen atoms to make a single sulfate ion. Because the starting ion name is sulf"ate", the final acid name becomes sulfur"ic" acid. If it had one less oxygen, it would be based on the sulf"ite" ion. That weaker version would be named sulfur"ous" acid instead. Car batteries use strong sulfuric acid to help store electrical energy.
Frequently asked questions
Why don't we use 'hydro' when naming ternary acids?
The 'hydro' prefix is a special rule saved only for binary acids. Binary acids only have two elements and no oxygen.
How do oxygen atoms make the acid stronger?
Oxygen is very greedy for electrons. It pulls electrons away from the hydrogen atom, which lets the hydrogen break off more easily.
What is the difference between sulfuric acid and sulfurous acid?
Sulfuric acid has four oxygen atoms and is very strong. Sulfurous acid only has three oxygen atoms and is much weaker.