What is the chemical name for the compound CuCO$_{3}$?

Step 1: Analyze the question We need the correct chemical name for CuCO₃. Copper is a transition metal that can have more than one oxidation state, so the name must show which one it has, using a Roman numeral.

Step 2: The concept

• The carbonate ion is CO₃²⁻ (charge of 2−).
• In an ionic compound, the total charge must be zero.
• For transition metals, the Roman numeral in the name = the charge (oxidation state) of the metal.

Step 3: Solution Let the charge on Cu be x:

x + (−2) = 0 x = +2

So copper is in the +2 oxidation state: Cu²⁺.

The name is therefore copper(II) carbonate.

Checking the other options:

• A. Copper(III) carbonate would need Cu³⁺, giving the formula Cu₂(CO₃)₃.
• C. Copper(I) carbonate would need Cu⁺, giving the formula Cu₂CO₃.
• D. "Copper" alone is just the element, not the compound.

Step 4: Answer The correct option is B. Copper (ii) carbonate.

Exam tip: For a compound of a transition metal, work out the Roman numeral by balancing the charges. Remember common ions: CO₃²⁻, SO₄²⁻ and O²⁻ are all 2−, NO₃⁻ and Cl⁻ are 1−. If the anion has a 2− charge and the formula has a 1:1 ratio, the metal is (II).