What notation is used in chemical formulas to show how many atoms of each element are present?

The notation used in chemical formulas to indicate the number of atoms of each element present in a compound is subscripts. In a chemical formula, subscripts are placed right after the chemical symbol of an element. For instance, in water (H₂O), the subscript "2" following the hydrogen symbol (H) signifies that there are two hydrogen atoms in each molecule of water. This notation provides essential information about the composition of the substance, allowing one to understand the ratio of different elements that make up the compound.

Other terms listed in the choices serve different purposes. Superscripts are typically used to denote charges in ionic compounds or isotopes, rather than the quantity of atoms. Indices generally refer to numerical indicators in mathematics or statistics, not specifically used in chemical context for counting atoms. Coefficients, on the other hand, appear in front of a formula to indicate the number of molecules in a chemical reaction, but they do not specify the number of atoms within those molecules. Thus, subscripts are the correct choice for this function in chemical notation.