Question

What is the chemical formula for the compound formed between chromium(III) and the sulfate ion?

Answer 1

do you know how it is the sulfate ion?

Answer 2

no

Answer 3

\[SO _{4}^{2-}\]

Answer 4

You already know that the Cr has a 2+ charge, the sulfate ion has a -2 charge.
you write the two ions with the charge and swap the charge of one has a sub-index of the other and vice versa without the charge symbol\[Cr ^{2+}SO _{4}^{2-}\]
\[Cr _{2}(SO _{4})_{2}\]
then you simplify to keep the smallest number possible
\[CrSO _{4}\]