In article , J. P. Gilliver (John)
wrote:
In message , Richard Tobin
writes:
In article , J. P. Gilliver
(John) wrote:

(Remember, of course, that all elements are radioactive, and have a
half life. It's just that most have such long half lives that we don't
normally _consider_ them radioactive.)

Really? Do you have a reference for that?

That is, for there being no completely stable isotopes?

-- Richard

Hmm, I thought I had, but on further investigation, it seems I'm
probably wrong - though I would argue that "stable" is not the same as
"has never been seen to decay".

Actually, it follows from the standard view of Quantum Mechanics that no
type of nucleus can be absolutely 'stable' - i.e. we can't guarantee it
will never 'decay' into something else. The point here is that any energy
bound system has an ongoing chance of suddenly parting due to QM effects.
Think of it as one part of the nucleus QM 'tunnelling' its way out of the
energy well/barrier of the system.

IIUC The only nominal exception as a nucleus is the hydrogen nucleus as it
is a single proton. But it is argued that even protons should sometimes
decay.

But as you say, in practice when the chance is very low, then the isotope
is assumed stable as the relevant long 'half llfe' values are meaninglessly
long for all practical purposes and may not have been measureable.

You can probably find a discussion of this in books on QM or nuclear
physics. But I dunno as I haven't had to read one in years! :-)

Slainte,

Jim

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