Final answer:
To name compounds with polyvalent cations, combine the name of the cation and the name of the anion. Do not use numerical prefixes except if the polyatomic ion itself contains a numerical prefix.
Step-by-step explanation:
The naming of ionic compounds that contain polyatomic ions follows the same rules as the naming for other ionic compounds: simply combine the name of the cation and the name of the anion. Do not use numerical prefixes in the name if there is more than one polyatomic ion; the only exception to this is if the name of the ion itself contains a numerical prefix, such as dichromate or triiodide.