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

[Allan Wechsler]

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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