Rules for chemical formulas
- Enter a sequence of element symbols followed by numbers to specify the amounts of desired elements (e.g., C6H6).
- Use correct case for element symbols. If correct case is not used, the formula may be ambiguous and the interpretation chosen may not be the desired one.
- Elements may be in any order.
- If only one of a given atom is desired, you may omit the number after the element symbol.
- Parentheses may be used to group atoms.
- Multiple specifications for an atom will be added. This means that CH3(CH2)4CH3will be treated the same as C6H14.
- To specify one or more of a given atom, use a question mark (?) after the element symbol.
- To specify any number (including zero) of given element, use an asterisk (*) after the element symbol.
- To explicitly specify an ion, place the charge at the end of the formula. If the charge is greater than one the charge should be included after the +or - symbol (e.g., C60-2).
Examples of chemical formulas
Chemical Formula | Search Specification |
C2H4 | Species with two C, and four H. |
CH2CH2 | Species with two C, and four H. |
CH3CH | Species with two C, and four H. |
(CH2)2 | Species with two C, and four H. |
C2H*F? | Species with two C, zero or more H and one or more F. |
Search options (step 2)
Exactly match the specified isotopes
When checked, this option indicates that the search should match isotopes as specified in the search formula. For example, when this option is not checked a search on H2 will match species containing deuterium and tritium atoms. If this option was checked, deuterium and tritium would be excluded from the search.
Allow elements not specified in formula
When checked, this option indicates that species containing elements not specified in the formula will also be matched. For example, a search for Te2 will find all of the species which contain exactly two tellurium atoms and any number of other atoms. Checking this option alone is equivalent to the "partial formula search" previously available from this site.
Allow more atoms of elements in formula than specified
This option indicates that species containg more atoms than specified of a given element will be matched. For example, a search for with only this option checked will find all tellurium, ditellurium, tritellurium, etc.
Exclude ions from the search
When this option is checked, the search will not match ions unless a charge is explicitly indicted in the formula.
Rules for data types (step 4)
- If one or more of the data types are checked, the search will be restricted to species which contain at least one of the data types specified.
- If none of the data types are checked, there will be no restrictions on the search.
