# Question #79da4

Apr 23, 2017

They all have a ratio of 1:1 for the number of positive ions to negative ions.

#### Explanation:

To consider the formulae of these ionic compounds, we must look at the charges on their respective ions formed.

Calcium forms a $C {a}^{2 +}$ ion since it has two valence electrons.

Carbonate: $C O {3}^{2 -}$
Oxide: ${O}^{2 -}$
Sulfite, or sulfate (IV): $S O {3}^{2 -}$
Sulfate, or sulfate (VI): $S O {4}^{2 -}$

Since all the anions here have charges of 2-, they form ionic compounds with $C {a}^{2 +}$ in the ratio 1:1.