What is the correct name for the ionic compound with the formula Cu_2S?

• A. Copper(I) sulfide
• B. Copper sulfate
• C. Copper(II) sulfide
• D. Copper(I) sulfate

Answer: (A)

Verified step by step guidance

1. Identify the cation and anion in the formula Cu_2S. Here, Cu represents copper (the cation) and S represents sulfur (the anion).
2. Determine the charge on the sulfur ion. Sulfur typically forms sulfide ions with a charge of 2-, written as S^{2-}.
3. Since the compound is neutral overall, the total positive charge from copper ions must balance the 2- charge from one sulfide ion. There are 2 copper atoms, so each copper ion must have a charge of +1 to balance the charge (2 × +1 = +2).
4. Name the cation using its element name and the charge in Roman numerals in parentheses. Since copper has a +1 charge here, it is named Copper(I).
5. Name the anion by taking the root of the element name and adding the suffix '-ide'. Sulfur becomes sulfide. Combine the names to get Copper(I) sulfide.