Complete the chemical name of the compound CoI3
The Correct Answer and Explanation is:
The chemical name of CoI₃ is Cobalt(III) iodide.
Explanation:
The compound CoI₃ consists of cobalt (Co) and iodine (I). The first step in naming the compound involves identifying the oxidation state of cobalt, as it can have multiple oxidation states. Cobalt typically forms two common oxidation states: +2 and +3.
To determine the oxidation state of cobalt in CoI₃, we consider the charges of the iodide ions. Each iodide ion (I⁻) has a charge of -1. Since there are three iodide ions in the compound, their total negative charge is -3. To balance this negative charge, cobalt must have a +3 charge, as the total charge of the compound must be zero. Therefore, cobalt is in the +3 oxidation state.
The name of the compound is formed by the name of the metal (cobalt) followed by its oxidation state in parentheses, and then the name of the anion (iodide). The iodine anion is named “iodide” because it is derived from the element iodine.
Thus, CoI₃ is named Cobalt(III) iodide.
Key Points:
- Cobalt’s oxidation state: +3 (as determined by balancing the charges of the iodide ions).
- Naming conventions: For transition metals with multiple oxidation states, the oxidation state is specified in Roman numerals in parentheses.
- Anion naming: Iodine becomes iodide (I⁻) in ionic compounds.
So, Cobalt(III) iodide is the correct chemical name for CoI₃.
