In inorganic nomenclature, what is the correct name for the compound with the formula Cu2CO3, based on the oxidation state of copper in this carbonate?

Introduction / Context:
Correctly naming ionic compounds requires understanding the charge balance between cations and anions as well as the oxidation states of transition metals. Copper can exhibit more than one oxidation state, so Roman numerals are used in names to show the charge on the metal ion. This question asks you to identify the correct name for Cu2CO3 and therefore determine the oxidation state of copper in this carbonate compound.

Given Data / Assumptions:

• Formula given: Cu2CO3.
• The carbonate ion has the formula CO3²⁻.
• Copper can form Cu⁺ (copper(I)) and Cu²⁺ (copper(II)) ions.
• The compound is assumed neutral overall.

Concept / Approach:
The approach is to apply charge balance. In an ionic compound, the total positive charge from the metal cations must balance the total negative charge from the anions. The carbonate ion carries a charge of 2⁻. The formula Cu2CO3 shows two copper atoms for each carbonate ion, so the combined positive charge from the two copper ions must be 2⁺ to balance the 2⁻ of carbonate. Dividing that positive charge by two gives the individual oxidation state of copper. Once the oxidation state is known, the correct stock name can be assigned using Roman numerals.

Step-by-Step Solution:
Step 1: Note that the carbonate ion CO3 has a charge of 2⁻. Step 2: The formula Cu2CO3 contains one CO3²⁻ ion and two Cu ions. Step 3: For overall charge neutrality, the sum of charges must equal zero, so total positive charge from copper ions must be 2⁺ to balance the 2⁻ from carbonate. Step 4: If the total positive charge from two copper ions is 2⁺, then each copper ion must have a charge of +1. Step 5: A copper ion with a +1 charge is copper(I), so the correct name is copper(I) carbonate.

Verification / Alternative check:
You can check by writing the compound as Cu⁺ and CO3²⁻ and then criss crossing the charges to get the formula. A 1⁺ cation and a 2⁻ anion will combine in a 2:1 ratio to give Cu2CO3. This matches the given formula and confirms the +1 oxidation state for copper. In contrast, copper(II) carbonate would be written as CuCO3 because Cu²⁺ and CO3²⁻ combine in a 1:1 ratio. This difference in formula between Cu2CO3 and CuCO3 is a useful way to distinguish the two oxidation states in carbonate compounds.

Why Other Options Are Wrong:
Option B, copper(II) carbonate, would correspond to CuCO3, not Cu2CO3. Option C, copper(III) carbonate, is not a common stable compound and would also not match the 2:1 ratio in the formula. Option D, basic copper carbonate, usually refers to compounds like Cu2CO3(OH)2, which include hydroxide as well as carbonate. Option E, copper hydrogen carbonate, would involve the hydrogen carbonate ion HCO3⁻ and would have a different formula. Only option A, copper(I) carbonate, correctly reflects the +1 oxidation state indicated by the Cu2CO3 formula.

Common Pitfalls:
Learners often assume that copper is always in the +2 state, leading them to choose copper(II) carbonate by habit. Another pitfall is forgetting to use charge balance and instead trying to guess based on typical names. Remember that the subscript numbers in formulas are linked to the charges on the ions. For transition metals that have variable oxidation states, always determine the charge from the formula before naming the compound.

Final Answer:
The correct IUPAC style name is Copper(I) carbonate, which corresponds to the formula Cu2CO3 with copper in the +1 oxidation state.