OptionalamountOptionalextensionAdditional content defined by implementations
OptionalidUnique id for inter-element referencing
OptionalmethodThe method by which the molecular weight was determined
OptionalmodifierExtensions that cannot be ignored even if unrecognized
OptionaltypeType of molecular weight such as exact, average (also known as. number average), weight average
Used to capture quantitative values for a variety of elements. If only limits are given, the arithmetic mean would be the average. If only a single definite value for a given element is given, it would be captured in this field