Final answer:
The subscript format is used in chemical formulas to denote the number of atoms, such as H2O for water, and the superscript format is used in mathematics to indicate exponents, like 4^2 for four squared.
Step-by-step explanation:
Two instances when subscript or superscript format should be used are in chemical formulas and in representing mathematical powers.
- Chemical Formulas: Subscripts are used to indicate how many atoms of a given element are present in a compound. For example, in water (H2O), the subscript '2' indicates there are two hydrogen atoms for every oxygen atom.
- Mathematical Powers: Superscripts are used to represent exponents in mathematics. For instance, the square of a number 4 would be written as 42.
It is important to remember that if the subscript is one, it is not written in the chemical formula, and to use the simplified subscript in the final formula.