Specific form of an element defined as to isotopic composition, electronic or oxidation state, and/or complex or molecular structure.
See also: chemical species
Source:
PAC, 2004, 76, 1033. 'Glossary of terms used in toxicokinetics (IUPAC Recommendations 2003)' on page 1044 (https://doi.org/10.1351/pac200476051033)