Final answer:
The charge of the nickel ion in the ionic compound Ni2O3 is +3. This is because there are three oxygen ions with a total negative charge of -6, so the nickel ion must have a positive charge of +3 to balance the charges.
Step-by-step explanation:
The charge of the nickel in the ionic compound Ni2O3 is +3. This is because each oxygen ion (O2-) has a charge of -2 and there are three oxygen ions, resulting in a total negative charge of -6. To balance this negative charge, the nickel ion (Ni) must have a positive charge of +3.