Misplaced Pages

Hill system

Article snapshot taken from Wikipedia with creative commons attribution-sharealike license. Give it a read and then ask your questions in the chat. We can research this topic together.

This is an old revision of this page, as edited by Phoebe (talk | contribs) at 22:45, 18 December 2009 (→References: + ref tag). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Revision as of 22:45, 18 December 2009 by Phoebe (talk | contribs) (→References: + ref tag)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)

The Hill system is a system of writing chemical formulas such that the number of carbon atoms in a molecule is indicated first, the number of hydrogen atoms next, and then the number of all other chemical elements subsequently, in alphabetical order. When the formula contains no carbon, all the elements, including hydrogen, are listed alphabetically.

By sorting formulas according to the number of atoms of each element present in the formula according to these rules, with differences in earlier elements or numbers being treated as more significant than differences in any later element or number — like sorting text strings into lexicographical order — it is possible to collate chemical formulas into what is known as Hill system order.

The Hill system was first published by Edwin A. Hill of the United States Patent and Trademark Office in 1900. It is the most commonly used system in chemical databases and printed indexes to sort lists of compounds.

Example

The following formulas are written using the Hill system, and listed in Hill order:

  1. BrH
  2. BrI
  3. CH3I
  4. C2H5Br
  5. H2O4S

A list of formulas in Hill system order is arranged alphabetically, as above, with single-letter elements coming before two-letter symbols when the symbols begin with the same letter (so C comes before Ca, which comes before Cl).

References

  1. ^ Wiggins, Gary. (1991). Chemical Information Sources. New York: McGraw Hill. p. 120.
  • Edwin A. Hill (1900). "On A System Of Indexing Chemical Literature; Adopted By The Classification Division Of The U. S. Patent Office". J. Am. Chem. Soc. 22 (8): 478–494. doi:10.1021/ja02046a005.

External link

  • Hill notation example, from the University of Massachusetts Lowell libraries, including how to sort into Hill system order
Category: