Question

How many oxygen atoms are in `Al_2(SO_4)_3`?

Answer 1

There are 12 oxygen atoms in `Al_2(SO_4)_3`.

Explanation:

In `Al_2(SO_4)_3`, the subscript of three next to the `SO_4` polyatomic ion refers to the number of that same ion is in this molecule. Since there are four atoms of oxygen in each `SO_4`, indicated by the subscript of four next to the oxygen, and there are three `SO_4` ions, `4*3= 12` oxygen atoms present in `Al_2(SO_4)_3`.