Final answer:
The correct name for the compound CuCO3 is copper(II) carbonate, denoting the copper ion has a 2+ charge.
Step-by-step explanation:
The compound CuCO3 is correctly named copper(II) carbonate. In naming ionic compounds where the metal can have more than one possible charge, we use Roman numerals to indicate the charge of the metal ion. Since copper can form cations with either a 1+ or 2+ charge, we need to specify which ion is present in the compound.
In this case, copper carbonate without a Roman numeral is not specific enough because copper can have two different oxidation states. We don't use copper(I) because the compound CuCO3 contains the copper(II) ion, indicated by the copper having a 2+ charge as it pairs with the carbonate ion (CO3) which has a 2- charge.