# What are the names of the following ionic compounds?

## $\text{FeO}$ ${\text{Fe"_2"O}}_{3}$ $\text{CaS}$ $\text{NaCl}$

Mar 27, 2017

Here;s what I got.

#### Explanation:

The thing to remember about ionic compounds that have Roman numerals in their name is that these numerals represent the oxidation state of the metal cation.

For iron(II) oxide, the $\left(\text{II}\right)$ Roman numeral tells you that you're dealing with an iron cation that carries a $2 +$ charge.

${\text{Fe}}^{2 +} \to$ the iron(II) cation

The oxide anion is formed when an oxygen atom gains two electrons, which implies that it carries a $2 -$ charge.

${\text{O}}^{2 -} \to$ the oxide anion

Keep in mind that ionic compounds are neutral, so always look to have a perfect balance between the overall positive charge on the cation and the overall negative charge on the anion.

In this case, you will have

["Fe"]^(2+) + ["O"]^(2-) -> "Fe"_ 2"O"_ 2

Therefore, you have

$\text{FeO } \to$ iron(II) oxide

For iron(II) oxide, the $\left(\text{III}\right)$ Roman numeral tells you that the iron cation carries a $3 +$ charge. This time, you will have

["Fe"]^color(red)(3+) + ["O"]^color(blue)(2-) -> "Fe"_ color(blue)(2) "O"_ color(red)(3)

Therefore, you can say that

${\text{Fe"_ 2"O}}_{3} \to$ iron(III) oxide

For calcium sulfide, keep in mind that calcium forms $2 +$ cations and sulfur forms $2 -$ anions, which means that you will have

["Ca"]^(2+) * ["S"]^(2-) -> "Ca"_ 2"S"_ 2

Therefore, you can say that

$\text{CaS } \to$ calcium sulfide

For sodium chloride, keep in mind that sodium forms $1 +$ carions and chlorine forms $1 -$ anions, which means that you will have

["Na"]^(+) + ["Cl"]^(+) -> "Na"_ 1"Cl" _1

Therefore, you can say that

$\text{NaCl } \to$ sodium chloride