How are parentheses used in chemical formulas? They are used to show atoms that are not part of the molecule. They are used to show which atoms are positively charged. They are used to show which atoms are most easily removed. They are used to show how atoms are grouped in the molecule.

One example of where you might see parentheses is the chemical, magnesium nitrate (Mg (N O3) 2). The parentheses are telling you that the whole N O3 bit is grouped together, and we have two of these units as determined by the outer subscript. It would not make sense to have notation for the atoms not in a molecule. Positive charges are indicated by superscripts +, 2+, etc. And the chemical equation tells the action of the atoms without needing a notation to indicate which is most easily removed.