Chemical Formulas

Chemical compounds are substances composed of two or more elements in specific proportions. To accurately describe these compounds chemical formulas were developed. 

The chemical formula provides information about the elements and the number of ions or atoms involved. Elements are depicted by their chemical symbol, while the relative number of ions or atoms is indicated with a subscript number. 

For example, table sugar or sucrose is a compound containing the elements carbon, hydrogen, and oxygen – represented using their symbols C, H, and O. The numbers 12, 22, and 11 indicate the total numbers of carbon, hydrogen, and oxygen atoms present within the compound.

In general, elements are not listed in alphabetical order, but rather starting with more positively charged, or metallic elements, followed by more negatively charged, or less metallic elements, like potassium hydroxide. 

Chemical formulas are categorized as molecular, empirical, and structural.

Molecular formulas describe a compound by listing each element and the exact number of atoms present. The molecular formula of glucose is C₆H₁₂O₆, meaning glucose is composed of six carbon, twelve hydrogen, and six oxygen atoms.

The empirical formula displays the simplest whole-number ratio of atoms of elements present. In glucose, the simplest ratio of carbon, hydrogen, and oxygen atoms is 1:2:1 — giving it the empirical formula CH₂O.

The molecular formula of a compound is also a whole-number multiple of its empirical formula. In glucose, the multiplication of its empirical formula with the whole-number six gives its molecular formula.

In contrast, the structural formula presents the relationship between the individual atoms graphically. The chemical symbols depict atoms, and short-lines denote chemical bonds. Single lines represent single bonds while two and three lines characterize double and triple bonds, respectively.

Extended models of the structural formula such as perspective drawing, ball-and-stick model, or the space-filling model, provide various three-dimensional perspectives about the molecular shape.

Amongst the three chemical formulas, a structural formula provides the most information about the chemical material, followed by the molecular formula. The empirical formula is the least informative.