# What is the formula for sodium sulfide?

Dec 30, 2015

$\text{Na"_2"S}$

#### Explanation:

When dealing with ionic compounds, it's important to know that the cation is always written first and the anion is written second.

In this case, sodium,$\text{Na}$, will be your cations and sulfide will be your anion.

Now, what exactly is a sulfide anion?

As you know, anions that consist of a single atom are named using the suffix -ide. Removing this suffix will give you the identity of the parent atom, which in this case is sulfur, $\text{S}$.

A quick look in the periodic table will show that sulfur is located in group 16, which means that it has a total of $6$ valence electrons.

To complete its octet, sulfur needs two more electrons. This means that the sulfur anion will carry a $2 -$ charge.

Since sodium is located in group 1 of the periodic table, it will lose its valence electron and form $1 +$ cations.

As you know, ionic compounds must be neutral. This means that you need two sodium cations to balance the negative charge of the sulfur anion.

The ionic formula for sodium sulfide will thus be

$\text{Na"_2"S}$

Sodium sulfide is a yellow in color, but aqueous solutions are colorless.