formula (chemistry)

In chemistry, a representation of a molecule, radical, or ion, in which the component chemical elements are represented by their symbols. For example, the formula for carbon dioxide is CO₂, showing that a molecule of carbon dioxide consists of one atom of carbon (C) and two atoms of oxygen (O₂). An empirical formula indicates the simplest ratio of the elements in a compound, without indicating how many of them there are or how they are combined. A molecular formula gives the number of each type of element present in one molecule. A structural formula shows the relative positions of the atoms and the bonds between them. For example, for ethanoic (acetic) acid, the empirical formula is CH₂O, the molecular formula is C₂H₄O₂, and the structural formula is CH₃COOH.