Tells how many of each atom there are in a formula

Explanation:

Subscripts are numbers written after elements, subscripts indicate how many of each atom there are in a compound.

The atoms of each element in an compund is written in the subscript. The number of atoms present in any compound whether made up of only same element or different element is termed as Atomicity.

Given compound =

Here, there are two atoms of hydrogen and one atom of oxygen, So ratio of the atoms of elements in Water molecule = 2 : 1

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