Editing Chemical formula (section)

=== Empirical formula ===
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In [[chemistry]], the [[empirical formula]] of a chemical is a simple expression of the relative number of each type of atom or ratio of the elements in the compound. Empirical formulae are the standard for [[ionic compound]]s, such as {{chem2|CaCl2}}, and for macromolecules, such as {{chem2|SiO2}}. An empirical formula makes no reference to [[isomer]]ism, structure, or absolute number of atoms. The term ''empirical'' refers to the process of [[elemental analysis]], a technique of [[analytical chemistry]] used to determine the relative percent composition of a pure chemical substance by element.

For example, [[hexane]] has a molecular formula of {{chem2|C6H14}}, and (for one of its isomers, n-hexane) a structural formula {{chem2|CH3CH2CH2CH2CH2CH3}}, implying that it has a chain structure of 6 [[carbon]] atoms, and 14 [[hydrogen]] atoms. However, the empirical formula for hexane is {{chem2|C3H7}}. Likewise the empirical formula for [[hydrogen peroxide]], {{chem2|H2O2}}, is simply {{chem2|HO}}, expressing the 1:1 ratio of component elements. [[Formaldehyde]] and [[acetic acid]] have the same empirical formula, {{chem2|CH2O}}. This is also the molecular formula for formaldehyde, but acetic acid has double the number of atoms.

Like the other formula types detailed below, an empirical formula shows the number of elements in a molecule, and determines whether it is a [[binary compound]], [[ternary compound]], [[quaternary compound]], or has even more elements.