What is the purpose of the Roman numeral within the name of an ionic compound?

• A. It indicates the charge of the metal cation.
• B. It shows the number of atoms of each element in the compound.
• C. It specifies the total number of ions present in the formula unit.
• D. It identifies the oxidation state of the nonmetal anion.

Answer: (A)

Verified step by step guidance

1. Understand that in ionic compounds, metals can often form more than one type of positive ion (cation) with different charges.
2. Recognize that the Roman numeral in the name of an ionic compound indicates the charge (oxidation state) of the metal cation in that compound.
3. Recall that this is important because the charge affects how the metal combines with the nonmetal anion to form a neutral compound.
4. Note that the Roman numeral does not indicate the number of atoms, total ions, or the oxidation state of the nonmetal anion.
5. Therefore, the Roman numeral helps distinguish between different ionic compounds formed by the same metal with different charges.