formula for copper (II) iodide
The Correct Answer and Explanation is:
Correct Formula: CuI₂
Copper (II) iodide consists of copper in the +2 oxidation state and iodide ions. Copper belongs to the transition metals, and it can exhibit multiple oxidation states. The Roman numeral (II) in the name indicates that copper has a +2 charge in this compound.
Iodine is a halogen and typically forms a -1 ion, known as the iodide ion (I⁻). To form a neutral compound, two iodide ions are needed to balance the +2 charge from one copper ion. Therefore, the combination results in a chemical formula of CuI₂.
However, copper (II) iodide is not stable under normal conditions. It tends to decompose into copper (I) iodide (CuI) and iodine (I₂). This happens because iodide ions are reducing agents and can reduce Cu²⁺ to Cu⁺, while themselves getting oxidized to elemental iodine. As a result, attempts to isolate pure copper (II) iodide often lead to this decomposition reaction:
2CuI₂ → 2CuI + I₂
Because of this instability, copper (II) iodide is rarely encountered in practice, and it is more common to see copper (I) iodide, which is stable and has the formula CuI.
Despite its instability, CuI₂ remains a valid chemical formula when considering oxidation states and ionic charges. In theoretical discussions and balanced chemical equations, the formula CuI₂ accurately represents a compound containing Cu²⁺ and I⁻ in a 1:2 ratio.
In summary, the formula CuI₂ arises logically by balancing the charges of Cu²⁺ and I⁻, even though the compound readily breaks down due to redox instability. This highlights the importance of both oxidation state knowledge and chemical stability considerations in understanding inorganic compounds.
