Talk:Monoisotopic element

Definition

The Commission on Atomic Weights and Isotopic Abundances (CAWIA) of IUPAC defines an element as monoisotopic "if it has one and only one isotope that is either stable or has a half-life greater than 1×10¹⁰ a" (see [1], p. 708, where also the list is presented: "The following 21 elements are considered to be monoisotopic in the evaluation of the atomic weights: Be, F, Na, Al, P, Sc, Mn, Co, As, Y, Nb, Rh, I, Cs, Pr, Tb, Ho, Tm, Au, Bi, and Th."). Thus, vanadium, rubidium, indium, lanthanum, europium, lutetium and rhenium should be removed from the list, and bismuth should be add. The radioactivity of several nuclides of these elements has nothing to deal with their natural occurrence. --V1adis1av (talk) 13:32, 31 March 2011 (UTC)[reply]

This commission does not distinguish between monoisotopic elements and mononuclidic elements, and says they are often used as synonyms. They may be, but sometimes they are not.[2]. The list you give, and this commission gives, is basically what we give as the 22 mononuclidic elements, which are those used in metrology (they list one less than we do, so that needs to be harmonized-- we're going to have to remove one or mark it as not recognized by IUPAC as of 2003). The problem with IUPAC's sloppy usage is that it leaves no word for the elements that have only one STABLE isotope (what we've called, and may others call monoisotopics-- they have ONE and only one stable isotope-- like beryllium but surely not like thorium-- or bismuth).

So I'll do two things: 10 remove one nuclide from the mononuclidic list, 2) add this reference and note that IUPAC sometimes uses "monoisotopic" to mean "mononuclidic" and that "monoisotopic" thus has TWO non-compatable definitions in use. Thanks for bringing this up. I think IUPAC should have addressed the point! S B H arris 18:31, 31 March 2011 (UTC)[reply]

Is there a reference for using monoisotopic to mean one isotope that does not have observed decay with any halflife? If not we shouldn't use it as such.

In every source I've seen so far "isotopes of element X" means either isotopes found in naturally occurring element X, or all observed isotopes no matter how unstable, or all possible isotopes. Excluding those that currently have been observed to decay even at rates that are insignificant over the life of the universe seems unintuitive, and the set will keep changing as more decays are observed.

I think the super-slow decays are a secondary topic that doesn't have to be in every single table of isotopes/nuclides, and clutters them up. In general, the naturally occurring isotopes are the set of interest, with some special treatment for those that have significant decay over the life of the universe. --JWB (talk) 22:46, 26 December 2011 (UTC)[reply]

Putting it another way, the distinction between observed super-long-halflife decay and theoretically predicted decay not yet observed, is a report of the current state of the art in one specialized field of research, that has nothing to do with almost all applications of elements or isotopes, and is also not stable over time. --JWB (talk) 22:55, 26 December 2011 (UTC)[reply]