# What is the charge on the theoretical element X that forms a cation with a oxygen and the formula of its oxide is X_2O?

Feb 9, 2016

$1 +$

#### Explanation:

The important thing to remember about ionic compounds is that they are electrically neutral.

This means that the overall positive charge coming from the cations must be balanced by the overall negative charge coming from the anions.

Now, your theoretical element $\text{X}$ forms an ionic compound with the oxide anion, ${\text{O}}^{2 -}$. This means that you need an overall positive charge of $2 +$ in order to balance the negative $2 -$ charge present on the oxide anion.

Notice that the formula of the compound is $\text{X"_2"O}$. This tells you that one formula unit of this oxide will contain

• two $\text{X}$ cations
• one ${\text{O}}^{2 -}$ anion

Well, if you have two $\text{X}$ cations that must have an overall charge of $2 +$, it follows that each $\text{X}$ cation will have a charge of $1 +$.

So, one formula unit for this oxide will contain two ${\text{X}}^{+}$ cations and one ${\text{O}}^{2 -}$ anion.