What is the chemical formula for aluminium oxide?

The chemical formula for aluminium oxide is represented as Al₂O₃, indicating that the compound is composed of two aluminium atoms and three oxygen atoms. This formula arises from the common oxidation states of aluminium and oxygen. Aluminium typically has a +3 charge, while oxygen generally has a -2 charge. To achieve charge neutrality in the compound, two aluminium ions (each with a +3 charge) balance out the three oxide ions (each with a -2 charge).

Mathematically, this can be expressed as:

2(+3) + 3(-2) = 0.

Thus, the correct ratio of aluminium to oxygen is provided by Al₂O₃. This compound is widely encountered in nature and is commonly known as corundum, which is found in minerals like sapphires and rubies.

The other choices do not correctly reflect the ratio of aluminium to oxygen needed to form a neutral compound.