Hey there!
2Fe₂O₃
Number of elements:
We see 2 atomic symbols in this formula: Fe and O. This means there are two elements.
Number of atoms:
There are 2 atoms of Fe because of the subscript of 2, and 3 atoms of O because of the subscript of 3. That is 5 atoms total, but there is a coefficient fo 2 in front, so we have twice as many. This means there are 10 atoms.
Number of atoms of Fe:
Like we said earlier, there are 2 atoms of Fe because of the subscript of 2, and there is a coefficient of 2 so we have twice that. This means there are 4 atoms of Fe.
Number of atoms of O:
Like we said earlier, there are 3 atoms of O because of the subscript of 3, and there is a coefficient of 2 so we have twice that. This means there are 6 atoms of O.
Hope this helps!