Final answer:
The correct formula for a compound formed between aluminum (Al) and oxygen (O) is Al2O3, which arises from the need to balance the charges of Al3+ and O2- ions in a 2:3 ratio to achieve electrical neutrality.
Step-by-step explanation:
The correct formula for a compound formed between aluminum (Al) and oxygen (O) is Al2O3. This is because in forming an ionic compound, the compound must be electrically neutral, balancing the positive and negative charges. Aluminum has a 3+ charge, represented as Al3+, and oxygen has a 2- charge, represented as O2-.
To balance these charges, we need two Al3+ ions for every three O2- ions, resulting in six positive charges and six negative charges. This charge balance yields the chemical formula Al2O3. Furthermore, the structural consideration indicates that there is one octahedral hole per oxide ion, and two-thirds of these holes are occupied by aluminum ions, which also supports the 2:3 ratio of aluminum to oxygen. Consequently, the formula Al2O3 correctly represents the stoichiometry of aluminum oxide.