Subscripts are used to indicate how many atoms of each element are present in a compound.

For example:

* H₂O (water) indicates that there are two hydrogen atoms (H) and one oxygen atom (O) in a water molecule.

* CO₂ (carbon dioxide) indicates that there is one carbon atom (C) and two oxygen atoms (O) in a carbon dioxide molecule.

Note:

* Subscripts are written after the element symbol.

* If there is only one atom of an element, the subscript is omitted.

* Subscripts can be used to represent both the number of atoms in a molecule and the number of moles of atoms in a compound.