unsigned int OEGetDefaultMass(unsigned int elemno)

Returns the most abundant isotope for the given atomic number i.e. the same values as required by the MDL file format. In MDL SD files, non-natural isotopes are represented as a delta from the most commonly occurring isotope for a particular element/atomic number.

For example, for OEElemNo_C this function returns the value 12. For input value of zero and for values greater than or equal to OEElemNo_MAXELEM, it returns zero.