[ghh (OP)]

I have been analysing Isotopes. I have copied data from various sources into a file, (which is much too big for an attachment, but I will send you a copy if you ask)
Generally, elements are classified with a particular crystal configuration; the question is whether this is true when the nuclear structure is different, e.g. 3He has different properties from 4He, and natural diamond with 1.1% 13C has different thermal conductivity to pure 12C.
Can we be sure that the geometry of an unstable isotope is the same as the stable Isotope of the same Z number?
Graham

[JimBob]

No - it is why unstable isotopes are unstable. In a crystal matrix either can bond but the difference in the atomic geometry causes the decay of the unstable isotope.

[ghh (OP)]

OK, but what if there are several stable isotopes with the same Z number,
as 56, 57 and 58 Fe?
Graham

[JimBob]

Same thing - they all fit in the matrix. The Z number indicates what possible matrix configuration the element has. But I learned this stuff 40 years ago SO .....

Being a geologist I am going to get a chemist involved in this discussion as well.

[Bored chemist]

The structures of molecules and crystals made from different isotopes are very nearly identical. The nuclei are (to a good aproximation) not involved in the bonding within, and between, molecules so the effects are tiny.
If they gave significantly different structures the separation of isotopes would be easy.

Also in most cases the stability  of the isotope is the same whether it's as an element, in a compound or whatever. (Does anyone really care about k capture half lives?)

[JimBob]

Thanks, John - very much appreciated.

[ghh (OP)]

Does John have an opinion on my post about decay energies?
Graham

[Bored chemist]

Yes, he does. It's this.
"Also in most cases the stability  of the isotope is the same whether it's as an element, in a compound or whatever. (Does anyone really care about k capture half lives?)"
The decay energy is practically independent of the environment of the nucleus.