* Al³⁺ is the correct symbol for the aluminum ion. It has a +3 charge.
Forming the Compound
To form an ionic compound, the charges of the ions must balance out to zero. Here's how it works:
1. Aluminum (Al³⁺) needs 3 chloride ions (Cl⁻) to balance its +3 charge: Since each chloride ion has a -1 charge, you need three of them to equal a -3 charge.
2. The formula is AlCl₃: This represents one aluminum ion (Al³⁺) and three chloride ions (Cl⁻).
Therefore, the formula for the ionic compound formed between aluminum and chloride is AlCl₃, which is called aluminum chloride.
