How do I predict the formula for the ionic compounds when I combine?

Question

Cr(+3) and chlorate
Na(+1) and carbonate
K(+1) andsulfate

Answer 1

Use the charges of the negative ions and make sure the charge of the compound equals zero.

Chlorate, carbonate and sulfate ions all have a charge of -2.

Potassium sulfate is K2SO4. Now you do the others.