Question

What are the names of the following ionic compounds?

`"FeO"`
`"Fe"_2"O"_3`
`"CaS"`
`"NaCl"`

Answer 1

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 `("II")` Roman numeral tells you that you're dealing with an iron cation that carries a `2+` charge.

`"Fe"^(2+) ->` the iron(II) cation

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

`"O"^(2-) ->` 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

`"FeO " ->` iron(II) oxide

For iron(II) oxide, the `("III")` 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

`"Fe"_ 2"O"_ 3 ->` 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

`"CaS " ->` 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

`"NaCl " ->` sodium chloride