The answer is subscript.
A chemical formula will give you information about what type of atoms and in what proportion make up a certain compound.
Take, for example, water,
The fact that you need
With the exception of 1, which is not written explicitly, any interger that follows an atom as a subscript will tell you exactly how many atoms of a certain type are found in a molecule.
Take a look at the molecular formula of sulfuric cid,
The subscripts that follow each type of atom will tell you exactly how many hydrogen, sulfur, and oxygen atoms are needed to form *1 molecule( of sulfuric acid. In this case, you have
- 2 atoms of hydrogen;
- 1 atom of sulfur (remember that 1 is not written explicitly);
- 4 atoms of oxygen.
One more example. Glucose has the molecular formula
- 6 atoms of carbon;
- 12 atoms of hydrogen;
- 6 atoms of oxygen.