Question

What will be the chemical formula for aluminium oxide?

• A. $A{l}_2{O}_3$
• B. $Al{O}_3$
• C. $AlO$
• D. $A{l}_2{O}_2$

Answer 1

The correct option is A $A{l}_2{O}_3$

1. Identify the symbols of the cation and anion

   Aluminium is Al and Oxide is O

2. Identify the charge for each and place above the symbol in parenthesis

   For Aluminium that would be 3+ and for Oxide that would be 2-

3. Balance the positive and negative charges

   Since each Aluminium is 3+ and each Oxide is 2- then it will take two Al⁺³ to balance 3 oxides with a 2- so that

   2(3+) + 3(2-) = 0. The numbers outside the parenthesis become the subscripts in the formula

4. Write the formula placing the subscripts right after the symbol they go with.
   Hence, the chemical formula for aluminium oxide can be written as $A{l}_2{O}_3$.