Optional
extensionOptional
halfHalf life - for a non-natural nuclide
Optional
idUnique id for inter-element referencing
Optional
identifierSubstance identifier for each non-natural or radioisotope
Optional
modifierExtensions that cannot be ignored even if unrecognized
Optional
molecularThe molecular weight or weight range (for proteins, polymers or nucleic acids)
Optional
nameSubstance name for each non-natural or radioisotope
Optional
substitutionThe type of isotopic substitution present in a single substance
Additional content defined by implementations