Ammonia, with the chemical formula NH3, is a compound that is commonly known as a base. However, it does not contain a hydroxyl group (-OH), which is a defining characteristic of most bases. This may seem contradictory, but there is a scientific explanation for this.


Before we delve into the reason why ammonia is a base without a hydroxyl group, let us first define what a base is. A base is a substance that can accept hydrogen ions (H+) or donate hydroxide ions (OH-) in a chemical reaction. Bases are often characterized by their slippery texture, bitter taste, and ability to turn red litmus paper blue.


Ammonia is a base because it has the ability to donate a lone pair of electrons to a proton (H+), forming a covalent bond. This process is known as protonation, and when it occurs, ammonia forms the ammonium ion (NH4+). This reaction is described by the equation:

NH3 + H+ → NH4+

The ammonium ion is a weak acid, as it can donate a proton in a chemical reaction. Ammonia’s ability to accept a proton and form the ammonium ion is what makes it a base.


Most bases contain a hydroxyl group (-OH), which donates hydroxide ions (OH-) in a chemical reaction. However, ammonia does not contain a hydroxyl group. This is because ammonia is a compound of nitrogen and hydrogen, and the nitrogen atom shares its lone pair of electrons with three hydrogen atoms, leaving no electrons to form a hydroxyl group. Therefore, ammonia cannot donate hydroxide ions like other bases.


In summary, ammonia is a base because it can accept a proton and form the ammonium ion. However, it does not contain a hydroxyl group because the nitrogen atom shares its lone pair of electrons with three hydrogen atoms, leaving no electrons to form a hydroxyl group.

Ammonia when dissolved in water it forms ammonium hydroxide.
Ammonium hydroxide readily ionizes to form ammonium ions (NH4+) and hydroxide ions (OH-). Thus the solution ammonia is considered as a base.
When ammonia dissolves in water it is believed that the ammonia accepts a hydrogen from the water due to the lone pair of electrons of the nitrogen in ammonia, this leaves an hydroxide ion that allows the solution to be basic.
A base is a proton acceptor. On the pH scale, bases have a pH greater than 7. Ammonia (NH 3 ) is a base because it can accept protons from water (H20) forming negatively charged hydroxide ions (OH-).

NH3(aq) + H2O(l) --> NH4+(aq) + OH-(aq)