Question

What part of the chemical formula indicates the number of molecules or atoms involved?

Answer 1

The subscript indicates the number of molecules/atoms in a formula.

Explanation:

For example, in `CO_2`, the 2 means there are 2 Oxygen atoms (`O`) in one molecule of the compound.

If a formula says `(NH_4)_2SO_4` or has similar parentheses, the subscript outside of the parentheses is how many of that part is in the compound (in this case - 2 `NH_4` ions).