# Question #f5310

Nov 22, 2015

${\text{NH}}_{4}^{+}$
${\text{H"_3"O}}^{+}$

#### Explanation:

The ammonium ion is formed when a molecule of ammonia, ${\text{NH}}_{3}$, accepts a proton, ${\text{H}}^{+}$.

This tells you two things

• the ammonium ion will have a total of four hydrogen atoms, one more than the ammonia molecule
• the ammonium ion will have an overall $\left(1 +\right)$ net charge coming from the added proton*

This means that the chemical formula for the ammonium ion will be

${\text{NH}}_{4}^{+}$

The hydronium ion is formed when a molecule of water, $\text{H"_2"O}$, accepts a proton, ${\text{H}}^{+}$.

This of course means that the hydronium ion will have three hydrogen atoms and a net overall charge of $\left(1 +\right)$. Its chemical formula will thus be

${\text{H"_3"O}}^{+}$

An alternative way of thinking about these ions is that they represent the conjugate acids of their respective bases, ammonia and water.

When a base accepts a proton from an acid, the compound that's formed is called a conjugate acid. In this case, the ammonium ion is the conjugate acid of ammonia and the hydronium ion is the conjugate acid of water.