Molecular Formulas

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Molecular formulas must be arranged in a standardized order called Hill System Order. Use either upper- or lowercase letters.

Substances Not Containing Carbon

Arrange the elements in alphabetical order, and indicate the number of each element present. If an element is present only once, no number is required. Examples:

• H2O4S
• CLH
• CL6SB

Substances Containing Carbon

Arrange with carbon first, hydrogen second (if present), then all other elements in alphabetical order. Examples:

• C8H18
• C2AG2N8
• C9H8CL4N8O

Parentheses in Molecular Formulas

If a molecular formula includes parentheses, you need to enclose the entire search term in quotes:

"(C2 H4 O)n C4 H6 O2"