What is the formula for copper(II) sulfide?

Copper(II) sulfide is a compound formed between copper and sulfur, specifically with copper in a +2 oxidation state and sulfur in a -2 oxidation state. In nomenclature, the Roman numeral II indicates that copper has a +2 charge.

To determine the correct formula, we first consider the charge of copper in this compound. Since copper has a +2 charge, and sulfur typically has a -2 charge, the charges balance out perfectly in a 1:1 ratio. Therefore, one copper ion combines with one sulfide ion to form the neutral compound.

Thus, the formula for copper(II) sulfide is CuS. In this formula, 'Cu' represents copper and 'S' represents sulfur. This reflects the balance of charges: one copper ion (Cu²⁺) pairs with one sulfide ion (S²⁻) to create a stable compound.

The other options don't accurately represent copper(II) sulfide based on this understanding of oxidation states and charge balancing. For instance, CuS2 implies a different oxidation state for copper than what is indicated by the Roman numeral II, while Cu2S suggests a composition of two copper atoms with one sulfide ion, which would imply a +1 oxidation state