American Chemical Society
Teaching Chemical Information:
Tips and Techniques
— August 1998 —
Hill System Order
Definition
Carbon first, Hydrogen second, and all remaining elements, including Deuterium and Tritium, in alphabetical order.
If no Carbon is present, put all elements in alphabetical order.
Indicate the number after each element symbol (ignore the fact that numbers are subscripts).
Search Tips
The molecular formulas in nearly all print and online files are arranged in Hill System Order.
Most resources are not case-sensitive (element symbols may be typed in upper or lower case letters). One exception is the Chapman and Hall Chemical Dicitionaries on CD-ROM. The molecular formula indexes in CHCD are case sensitive.