edit – history – watch – refresh
I do not believe that this term belongs in physics at all, but rather in chemistry. The term is a practical one used as an aid to mass spectrometry and does not correspond to any useful physical concept.
The discussion regarding why the lightest isotope is not the most abundant assumes that the reader expects it to be the most abundant. The innocent bystander wouldn't; nor would the expert. I think a few graphics would improve the explanation. I did not edit past the first P.