The Empirical formula reference article from the English Wikipedia on 24-Apr-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Empirical formula

In chemistry, the empirical formula of a chemical is a simple expression of the relative number of each type of atom (element) in it. An empirical formula makes no reference to isomerism, structure, or absolute number of atoms. The term empirical refers to the process of elemental analysis, an analytical technique used to determine the relative percent composition of a pure chemical substance by element.

For example, hexane could have a chemical formula of CH₃CH₂CH₂CH₂CH₂CH₃, implying that it has a straight chain structure, 6 carbon atoms, and 14 hydrogen atoms. However the empirical formula for the same molecule would be C₃H₇.

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In physics, an empirical formula is a mathematical equation that predicts observed results, but has no known theoretical basis to explain why it works.

An example was the Rydberg formula to predict the wavelengths of hydrogen spectral lines. Proposed in 1888, it perfectly predicted the wavelengths of the Lyman series, but until Niels Bohr produced his Bohr model of the atom in 1913, nobody knew why the formula worked.

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