What is the chemical formula for calcium iodide?

The chemical formula for calcium iodide is represented as CaI2. This formula indicates that one calcium ion (Ca²⁺) combines with two iodide ions (I⁻) to form a neutral compound. Calcium is an alkaline earth metal that has a +2 charge when it forms ions. Iodine, a halogen, typically forms ions with a -1 charge.

To achieve electrical neutrality in the compound, two iodide ions are required for every calcium ion, leading to the formula CaI2. This stoichiometry ensures that the charges balance: the +2 charge from calcium is balanced by the -1 charge from each of the two iodine atoms, giving a total of -2 from the iodide ions. This combination results in a stable ionic compound.

The other options do not provide the correct balance of charges necessary for neutrality in calcium iodide. For example, CaI would not satisfy the charge balance because it would still have a net positive charge. Similarly, formulas like Ca2I and CaI3 suggest incorrect stoichiometric ratios that do not correspond to the actual relationship between calcium and iodide in this compound.