formula weight

formula weight

noun

Definition of FORMULA WEIGHT

:  molecular weight —used especially of ionic compounds

First Known Use of FORMULA WEIGHT

circa 1920

formula weight

noun    (Concise Encyclopedia)

Sum of the atomic weights of all atoms in a chemical formula. The term is generally applied to a substance that consists of ions (see ionic bond) rather than individual molecules (and thus does not have a molecular weight). An example of such a substance is sodium chloride (table salt). Such a substance's chemical formula describes the simplest ratio of the number of atoms of the constituent elements. See also stoichiometry.