In this problem, we want to find the IUPAC name for NiCO3. Again the first question that we always ask ourself is this molecular or ionic? I noticed that I have Nickel which is a metal. And Carbonate, which is a polyatomic ion. And so, this indicates that I'm dealing with an ionic compound. And so, I'm going to have to name it accordingly. Now also notice that Nickel is a transition metal, which means I have to indicate in the name what the charge is on the Nickel. So let's look at first assigning the charge to the Nickel before we write the name. Now I know I have one Nickel ion with some charge that we're going to call x,. Plus one Carbonate ion, and the charge on that is two minus. Because this is a neutral compound, the sum of those ionic charges should sum to zero. And so I can actually just solve for x, and find that the charge on the Nickel was going to be two plus. Now, I can write the name of my compound. And I'm going to say nickel. And in parentheses I'm going to put the Roman numeral II and then the name of my anion my carbonate. A couple of things to note here one these are Roman numerals indicating the charge on the nickel. There's no space between the name of the metal and the opening parentheses. We don't change the ending of the carbonate because it's a polyatomic ion we use those names as is. Remember that the only three transition metals that we do not use Roman numerals for. Are Silver, which has a plus one charge, Zinc has two plus, and Scandium, which has a three plus. Because, for those three transition elements, there's really only one possible charge. So a Roman numeral is not needed. All other transition metals will get the Roman numeral.