[seqfan] Re: Atomic number of n-th element in the "neptunium series"

[Allan Wechsler]

The proposed sequence was not just counting down by fours. Every nucleus
contains integral numbers of protons and neutrons. The mass number is the
sum of these two; it is this that does not change (modulo 4) during
radioactive decay. The atomic number is just the number of protons. Each
decay event can change the atomic number by -2, -1, or +1, depending on
what kind of decay it is. I believe Felix Fröhlich was proposing recording
the atomic numbers in a sequence.


On Thu, Apr 19, 2018 at 11:18 AM, Neil Sloane <njasloane at gmail.com> wrote:

> If the sequence is just counting down by 4's from 149, it probably is not
> worth adding to the OEIS
>
> Best regards
> Neil
>
> Neil J. A. Sloane, President, OEIS Foundation.
> 11 South Adelaide Avenue, Highland Park, NJ 08904, USA.
> Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ.
> Phone: 732 828 6098; home page: http://NeilSloane.com
> Email: njasloane at gmail.com
>
>
> On Thu, Apr 19, 2018 at 7:52 AM, Allan Wechsler <acwacw at gmail.com> wrote:
>
> > Every nucleus has an integer mass number; radioactive decay either
> doesn't
> > change the mass number, or reduces it by 4. Therefore, there are four
> > classes of radioactive nuclei. The Np-237 series all have mass number of
> > the form 4n+1. It is called the Neptunium series because at the time of
> its
> > discovery, Neptunium was the earliest known member. Four prior members
> are
> > now known: Californium-249, Curium-245, Plutonium-241, and Americium-241
> > (which decays into Neptunium-237).
> >
> > The 4n series's earliest known member is Californium-252 and is called
> the
> > Thorium series; 4n+2 starts with Uranium-238 and is named after it; and
> > 4n+3 starts with Californium-251 and is called the Actinium series.
> >
> > I have no opinion on whether the atomic numbers of these series belong in
> > OEIS; they seem like a borderline case to me.
> >
> > On Thu, Apr 19, 2018 at 6:31 AM, Felix Fröhlich <felix.froe at gmail.com>
> > wrote:
> >
> > > "Why Neptunium 237?"
> > >
> > > I chose it because it seems to have a long decay chain. There may be
> > other
> > > lements with longer chains, I am not sure. Also, I thought it was
> > > interesting that the chain cannot have progressed past Bi-209 naturally
> > due
> > > to the extremely long half-life of Bi-209.
> > >
> > > Thanks for your suggestion regarding making each term the number of the
> > > most common element. That sounds like a good idea.
> > >
> > > Regards
> > > Felix
> > >
> > > 2018-04-19 1:55 GMT+02:00 Frank Adams-watters via SeqFan <
> > > seqfan at list.seqfan.eu>:
> > >
> > > > If this is added, I think each term should be the atomic number of
> the
> > > > most common element at that step.
> > > > This "stabilizes " the sequence: otherwise at step n, if you
> discovered
> > > > their was another decay product
> > > > occurring only with, say, probability 0.001%, the sequence would have
> > to
> > > > be changed so that a(n) = 0.
> > > >
> > > > Second, why Neptunium 237? Is there something special about it?
> > > >
> > > > Franklin T. Adams-Watters
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: Felix Fröhlich <felix.froe at gmail.com>
> > > > To: Sequence Fanatics Discussion list <seqfan at list.seqfan.eu>
> > > > Sent: Wed, Apr 18, 2018 7:41 am
> > > > Subject: [seqfan] Atomic number of n-th element in the "neptunium
> > series"
> > > >
> > > > Dear SeqFans,here is an idea for a sequence related to radioactive
> > decay
> > > > of a chemical
> > > > element:
> > > > Atomic number of n-th element in the "neptunium series", the decay
> > chain
> > > of
> > > > neptunium-237, or 0 if the n-th link of the chain consists of more
> than
> > > one
> > > > element. For an overview, please see
> > > > https://en.wikipedia.org/wiki/Decay_chain#Neptunium_series
> > > > The sequence starts 93, 91, 92, 90, 88, 89, 87, 85, 83, 0, 82, 83,
> > > 81a(10)
> > > > (if the offset is 1) is 0, because bismuth-213 decays into
> > > > polonium-213 and thallium-209, both of which in turn decay into
> > lead-209.
> > > > I don't know if this sequence is interesting. The "0" term may be a
> bit
> > > > unsatisfactory, but I am not sure of a better way to resolve the
> issue
> > of
> > > > an
> > > >  isotope decaying into two daughter isotopes at the moment.
> > > >
> > > > Best regardsFelix Fröhlich
> > > >
> > > > --Seqfan Mailing list - http://list.seqfan.eu/
> > > >
> > > > --
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> > >
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> >
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