How to calculate the atoms of each element in Fe2 (SO4)3?
And an explanation on how to calculate for other formulas.
SO4 has 5 atoms
so (SO4)3 has 5*3 = 15 atoms
Now just add the 2 Fe atoms, and you have 17 atoms per molecule
2 Fe
3*1 = 3 S
3*4 = 12 O
You can't get a better answer than oobleck gave you for Fe2(SO4)3.
Here is how you do ANY formula. For example, 2Mg(ClO3)2.
The number AFTER the element multiplies just that element; i.e., Mg is 1, Cl is 1, O is 3. The number AFTER a set of parentheses multiplies everything within the parentheses; i.e., Cl is 2, O is 6. A number BEFORE the formula multiplies everything that follows by that number; i.e., Mg is 2 (2*1), Cl is 4 (2*2) and O is 12 (2*6).