Chemical Formulas - Isotopes

Isotopes

Although isotopes are more relevant to nuclear chemistry or stable isotope chemistry than to conventional chemistry, different isotopes may be indicated with a prefixed superscript in a chemical formula. For example, the phosphate ion containing radioactive phosphorus-32 is 32PO₄3-. Also a study involving stable isotope ratios might include the molecule 18O16O.

A left-hand subscript is sometimes used redundantly to indicate the atomic number. For example, ₈O₂ for dioxygen, and 16₈O₂ for the most abundant isotopic species of dioxygen. This is convenient when writing equations for nuclear reactions, in order to show the balance of charge more clearly.