Ionic Compounds with Polyatomic Ions
The third type of ionic compounds is ionic compounds with polyatomic ions. The basic compounds of this type contain three elements: the positive ion, and two elements joined together to act as the negative ion. One exception to this is ammonium, which has a + charge.
Unfortunately, there is no set “rule” on naming polyatomic ions; to know the name, you would have to have a list with the names. With these compounds, the names of both ions stay the same, so if you were given Al2(CO3)2, you would keep the first as aluminum, and CO3 is carbonate, and you keep that as carbonate, with the full name as aluminum carbonate.
if you were to write the chemical formula of a given compound, you will most likely need a list with the basic polyatomic ions, as you will need to know the ion charges.
A quiz to practice naming ionic compounds with polyatomic ions: http://www.proprofs.com/quiz-school/story.php?title=ionic-compound-names-formulas-quiz-2
CuSO4 - Copper(II) sulfate