7
In 2Fe2O3, there are a total of 10 atoms: 4 iron atoms (2 x 2) and 6 oxygen atoms (2 x 3).
There are no iron atoms in oxygen. Oxygen is an element in itself so it can not be complicated by another element unless it becomes a molecule of something else. Usually iron that has been mixed with oxygen can be form an iron oxide.
There are two atoms of iron and three atoms of oxygen in the compound Fe2O3. The mass percent of iron is 69.943%
The chemical formula shows you this. The subscripted number next to each element shows how many atoms are present in a molecule or formula unit. If no number is shown, then only one atom of that element is present.
You can determine the number of atoms of each element in a compound by using the chemical formula of the compound. The subscripts in the formula indicate the number of atoms of each element. For example, in H2O (water), there are 2 hydrogen atoms and 1 oxygen atom.
there are 3 in tottal
2
Some elements have isotopes - atoms with a different number of neutrons.
If its just iron then there is only one type of atom: iron atoms
1
In each molecule of NO3, there is one nitrogen atom and there are three oxygen atoms.
a. 1 iron atom per molecule. in total, two atoms