Final answer:
Aluminum oxide, or Al2O3, has two aluminum ions with a 3+ charge and three oxygen ions with a 2- charge, which cancel each other out, resulting in a neutral compound.
Step-by-step explanation:
To show that the positive and negative charges in a unit of Al2O3 equals zero, we need to consider the charges on aluminum (Al) and oxygen (O) ions. Aluminum typically forms a 3+ charge, while oxygen typically forms a 2- charge. In aluminum oxide, or alumina, there are two aluminum ions for every three oxygen ions.
Each aluminum ion has a 3+ charge, and there are two of them, which totals 6+ (2 × 3+). Each oxide ion has a 2- charge, and with three of them, the total charge becomes 6- (3 × 2-). When you combine these charges from the aluminum and oxygen ions, they cancel each other out:
(2 × +3) + (3 × -2) = +6 + (-6) = 0.
Thus, the compound Al2O3 is electrically neutral, indicating that the total numbers of positive and negative charges are balanced.