What is the correct systematic IUPAC name for the ionic compound with the formula CuI, which contains copper and iodide ions?

Introduction / Context:
Systematic naming of ionic compounds using IUPAC rules helps chemists communicate clearly about substances with different oxidation states and compositions. The formula CuI represents a compound containing copper and iodide ions, and the correct name must reflect the charge on copper. This question tests your understanding of the naming conventions for transition metal halides and the use of Roman numerals in IUPAC nomenclature.

Given Data / Assumptions:

• Chemical formula: CuI.
• Elements present: copper (Cu) and iodine (I) as iodide.
• Iodide ion typically carries a charge of 1 minus.
• Copper can exhibit more than one oxidation state, commonly 1 plus and 2 plus.

Concept / Approach:
In binary ionic compounds, the metal is named first followed by the nonmetal with the ending changed to ide. When the metal can have more than one oxidation state, the specific oxidation state is indicated using a Roman numeral in parentheses after the metal name. In CuI, iodide has a charge of 1 minus, so copper must be in the 1 plus state to balance the charge. Therefore, the correct IUPAC name is copper(I) iodide, with the Roman numeral I indicating the copper oxidation state.

Step-by-Step Solution:
Step 1: Recognize that iodide, I minus, has a charge of 1 minus in ionic compounds. Step 2: Note that the formula CuI has a one to one ratio of copper ions to iodide ions. Step 3: For charge neutrality, the copper ion must have a charge of 1 plus, since 1 plus from copper and 1 minus from iodide balance. Step 4: According to IUPAC rules, name the metal first, including its oxidation state in parentheses, then name the nonmetal as iodide. Step 5: Combine these to get the name copper(I) iodide as the correct systematic name.

Verification / Alternative check:
If copper were in the 2 plus state with iodide, the formula would be CuI2 to balance charges, and the name would be copper(II) iodide. Since the given formula is CuI, not CuI2, copper must be in the 1 plus state. Looking at other copper compounds, such as Cu2O (copper(I) oxide) and CuO (copper(II) oxide), reinforces the pattern that the Roman numeral indicates the positive charge. This verification confirms that copper(I) iodide is the correct name for CuI.

Why Other Options Are Wrong:
Option B, cobalt fluoride, refers to a different metal and a different anion, and does not match the CuI formula. Option C, ferrous oxide, is an older name for iron(II) oxide and again involves a different metal and oxygen rather than iodide. Option D, all of the above, cannot be correct because options B and C clearly describe different compounds. Only option A correctly names the compound CuI in systematic IUPAC style.

Common Pitfalls:
A common mistake is to ignore the possibility of multiple oxidation states and write simply copper iodide without indicating the charge. While this may be acceptable in some informal contexts, systematic naming requires the Roman numeral when the metal can have more than one common oxidation state. Another pitfall is mixing up formulas and names of similar looking compounds, such as confusing CuI with CuI2. Carefully matching the formula to charges and using the rules for Roman numerals helps avoid these errors.

Final Answer:
The correct systematic IUPAC name for CuI is copper(I) iodide.